The interpretation timeline
Genesis 4:4 Douay-Rheims

Abel also offered of the firstlings of his flock, and of their fat: and the Lord had respect to Abel, and to his offerings.

A.D. 45 – 1871 11 witnesses

Patristic

before A.D. 750
45
A.D.
c. 15 B.C.–A.D. 45
“(60) Why Cain after some days offers up the first-fruits of his fruits, but when it is said that "Abel offered up first-fruits of the first-born of his flock and of the fat," "after some days" is not added? (#Ge 4:3-4). Moses here intimates the difference between a lover of himself, and one who is thoroughly devoted to God; for the one took to himself the first-fruits of his fruits, and very impiously looked upon God as worthy only of the secondary and inferior offerings; for the expression, "after some days," implies that he did not do so immediately; and when it is said that he offered of the fruits, that intimates that he did not offer of the best fruits which he had, and herein displays his iniquity. But the other, without any delay, offered up the first-born and eldest of all his flocks, in order that in this the Father might not be treated unworthily.”
Source
99
A.D.
Clement of Rome Patristic
d. A.D. 99
“Every kind of honour and happiness was bestowed upon you, and then was fulfilled that which is written, "My beloved ate and drank, and was enlarged and became fat, and kicked." [Deuteronomy 32:15] Hence flowed emulation and envy, strife and sedition, persecution and disorder, war and captivity. So the worthless rose up against the honoured, those of no reputation against such as were renowned, the foolish against the wise, the young against those advanced in years. For this reason righteousness and peace are now far departed from you, inasmuch as every one abandons the fear of God, and has become blind in His faith, neither walks in the ordinances of His appointment, nor acts a part becoming a Christian, but walks after his own wicked lusts, resuming the practice of an unrighteous and ungodly envy, by which death itself entered into the world. [Wisdom 2:24] For thus it is written: "And it came to pass after certain days, that Cain brought of the fruits of the earth a sacrifice unto God; and Abel also brought of the firstlings of his sheep, and of the fat thereof. And God had respect to Abel and to his offerings, but Cain and his sacrifices He did not regard. And Cain was deeply grieved, and his countenance fell. And God said to Cain, Why are you grieved, and why is your countenance fallen? If you offer rightly, but do not divide rightly, have you not sinned? Be at peace: your offering returns to yourself, and you shall again possess it. And Cain said to Abel his brother, Let us go into the field. And it came to pass, while they were in the field, that Cain rose up against Abel his brother, and slew him." [Genesis 4:3-8] You see, brethren, how envy and jealousy led to the murder of a brother. Through envy, also, our father Jacob fled from the face of Esau his brother [Genesis 27:41-45]. Envy made Joseph be persecuted unto death, and to come into bondage. [Genesis 37:18-28] Envy compelled Moses to flee from the face of Pharaoh king of Egypt, when he heard these words from his fellow-countryman, "Who made you a judge or a ruler over us? Will you kill me, as you killed the Egyptian yesterday?" [Exodus 2:14] On account of envy, Aaron and Miriam had to make their abode without the camp. [Numbers 12:14-15] Envy brought down Dathan and Abiram alive to Hades, through the sedition which they excited against God's servant Moses. [Numbers 16:33] Through envy, David not only underwent the hatred of foreigners, but was also persecuted by Saul king of Israel. [1 Samuel 21:10-15]”
Source
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“It was not idly or in vain that in beginning this sermon we taught your good selves that our Lord does not recognize differences in appearance but takes account of intentions and rewards the will. Here, too, to be sure, notice this happening. Accordingly, let us attend with precision, dearly beloved, to the text and see what Scripture says about Cain on the one hand and Abel on the other, and let us not pass it by heedlessly. I mean, Sacred Scripture says nothing idly or by chance; instead, even if it happens to be a syllable or a single jot, it has some treasure concealed in it. Such, after all, is the nature of all things spiritual. So what does the text say? "In the course of time Cain brought an offering of the fruits of the earth to the Lord, and Abel also for his part brought an offering of the firstborn of his flock, and in fact the fattest of them." The meaning of the verse is clear even from the reading to those already capable of following more closely. But since we should exercise our concern in general for everyone (spiritual teaching, after all, recognizes no distinction), come now, let us expose the meaning of the words more clearly and rehearse these same words again. "Cain," the text says, "brought an offering of the fruits of the earth to the Lord"; then, wanting to teach us about Abel as well, Sacred Scripture says that he for his part also brought his offering [155] from his occupation and his shepherding. "He, for his part, also brought an offering," the text says, remember, "of the firstborn of his flock, and in fact the fattest of them." Notice how it hints to us of the piety of this man's attitude, and the fact that he did not casually offer any one of his sheep, but "one of the firstborn," that is, from the valuable and special ones. In Cain's case, on the contrary, nothing of the kind is suggested; rather, the fact that he brought "an offering of the fruits of the earth," as if to say, whatever came to hand, without any display of zeal or precise care. I repeat, and I shall not cease to make the point: God accepts our offerings not because he needs what we have to offer but because he wants our gratitude to be demonstrated through them as well. In other words, the person who makes an offering to God and offers him something of his own, and who calls to mind the difference in nature and the fact that a human being has been granted such a great honor, should give as good an account of himself as possible and offer the choicest gifts. But notice in this case, I ask you, dearly beloved: here you have the opportunity to contemplate what behooves you, namely, that the person who through indifference betrayed his own welfare duly pays the penalty. I mean, it wasn't a case of one man having a teacher and the other having a counsellor and adviser: each had instructions from his own conscience, and being moved by the intelligence supplied to the human race from above he proceeded to make his offering, such as it was; but the difference in attitude that emerged and the mediocrity of choice caused one man's offering to be acceptable and the other's to be spurned. "God took notice of Abel and his conscience. Aftthis case is fulfilled the saying in the gospel that the first will be last and the last first.'-~ I mean, see how the one who enjoyed priority belonging to the firstborn and consequently made his offering first was shown to be inferior to his brother since he made it unworthily: as both presented their offerings, Sacred Scripture says, "God took notice of Abel and his gifts." What does that mean, "He took notice"? He accepted, he approved of the attitude, he rewarded the choice, he was satisfied (so to say) with what was done. You see, we speak about God and presume to open our mouth about that pure nature, yet being human we would have no choice but to understand these things through language. Notice, however, this remarkable feature: "God took notice of Abel and his gifts," the text says; it calls the offering of sheep gifts on account of the importance, the choice quality, the untainted appearance of what was offered. Accordingly, God took notice of him for the reason that he had made the offering with a pure intention, and of his gifts for the reason not only that they were free of imperfection but that they were in every respect clearly precious, both from the viewpoint of the offerer's intention and from the fact of their being the firstborn and in fact specially selected from them, among the fattest of them and the very prize ones.”
Source
430
A.D.
Augustine of Hippo Patristic
A.D. 354–430
“[The pagans say, "The Christians] censure the ceremonies of sacrifice, the victims, incense and the rest, which are used in temple worship. Yet the same ceremonies of sacrifice were originated by themselves or by the god they worship, in primitive times, when a god was assumed to need their offerings of first fruits." This question is evidently derived from that passage in our Scriptures that tells of Cain making an offering to God of the fruits of the earth and Abel of the firstlings of his flocks. We answer that the conclusion to be drawn from it is that sacrifice is a very ancient custom, because our true and sacred Books warn us that it is not to be offered except to the one true God. But God does not need sacrifices, as is most clearly expressed in the same sacred Books: "I said to the Lord, thou art my God, for thou hast no need of my goods," because in accepting or refusing or receiving them he is looking only to man's good. God does not derive any benefit from our worship, but we do.”
Source
523
A.D.
c. A.D. 450–523
“And moreover, we may also see simplicity in Abel, and the Holy Book sheweth us that he was more simple than Cain; for they both brought offerings to the Lord, and the offering of simplicity was accepted, but the offering of wickedness was rejected. And Cain was angry with the Lord and with Abel; with Abel because he envied him, and with the Lord because He had rejected his offering. If he had been of a simple disposition he would not have been envious, and if he had been sincere he would not have been angry with the Lord.”
Source
date
unknown
c. A.D. 550
“If it is true that before the Flood they did not eat flesh, why is it then written: Abel was a keeper of sheep, and brought of the firstlings of his flock and of the fat thereof? If they did not eat flesh, why did they take upon them the care of sheep? And why did Abel, when he brought a lamb for sacrifice, not slay it? Now, one who so enquires, will be truly answered that, in making the oblation, he presented the holocausts alive; for one of the editions shows this, saying: Over Cain and over his sacrifice he did not apply fire, so that it is evident that the offerings were consumed with divine fire. They provided themselves with a flock to procure for themselves milk and wool. Another objection: If they did not eat flesh, how came it into their head to select the fat for the sacrifice to God? Answer—Because when anything is to be burned in the fire, fat is more readily set ablaze”
Source

Scholastic

c. 1100 – 1500
1105
A.D.
Rashi Jewish
1040–1105
וישע AND HE HAD REGARD— and He turned to; similarly in the next verse “He had no respect for his offering” means, “He did not turn to it.” Similarly, (Isaiah 17:8) ולא ישעה אל המזבחות which means “And he shall not turn towards the altars”; so also (Job 14:6) שעה מעליו “turn away from him” — disregard him. וישע AND HE HAD REGARD — Fire descended from heaven and consumed his offering.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“And Abel, he also brought of the firstlings of his flock,.... As he was a shepherd, his flock consisted of sheep; and of the firstlings of these, the lambs that were first brought forth, he presented as an offering to the Lord; and which were afterwards frequently used in sacrifice, and were a proper type of Christ, Jehovah's firstborn, the Lamb of God that takes away the sin of the world, a Lamb without spot and blemish; fitly signified by one for his innocence, harmlessness, and meekness: and of the fat thereof; which is to be understood either of the fat properly, which in later time was claimed by the Lord as his own, Lev 3:16 or of the fattest of his flock, the best lambs he had; the fattest and plumpest, and which were most free from defects and blemishes; not the torn, nor lame, nor sick, but that which was perfect and without spot; for God is to be served with the best we have. Josephus (f) says it was milk, and the firstlings of his flock; and a word of the same letters, differently pointed, signifies milk; and some learned men, as Grotius and others, have given into this sense, observing it to be a custom with the Egyptians to sacrifice milk to their gods: but the word, as here pointed, is never used for milk; nor were such sacrifices ever used by the people of God; and Abel's sacrifice is called by the apostle a "slain" sacrifice, as Heidegger (g) observes: and the Lord had respect to Abel, and to his offering; as being what he had designed and appointed to be used for sacrifice in future time, and as being a suitable type and emblem of the Messiah, and his sacrifice; and especially as being offered up by faith, in a view to the sacrifice of Christ, which is of a sweet smelling savour to God, and by which sin only is atoned and satisfied for, see Heb 11:4. God looked at his sacrifice with a smiling countenance, took, and expressed delight, well pleasedness, and satisfaction in it; and he first accepted of his person, as considered in Christ his well beloved Son, and then his offering in virtue of his sacrifice: and this respect and acceptance might be signified by some visible sign or token, and particularly by the descent of fire from heaven upon it, as was the token of acceptance in later times, Lev 9:24 and Theodotion here renders it, he "fired" it, or "set" it on "fire"; and Jarchi paraphrases it,"fire descended and licked up his offering;''and Aben Ezra,"and fire descended and reduced the offering of Abel to ashes;''so Abraham Seba (h). (f) Antiqu. l. 1. c. 2. sect. 1. (g) Hist. Patriarch. Exercit. 5. sect. 20. (h) In Tzeror Hammor, fol. 8. 2.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“Abel, he also brought of the firstlings of his flock - Dr. Kennicott contends that the words he also brought, הביא גם הוא hebi gam hu, should be translated, Abel brought it also, i.e. a minchah or gratitude offering; and beside this he brought of the first-born (מבכרות mibbechoroth) of his flock, and it was by this alone that he acknowledged himself a sinner, and professed faith in the promised Messiah. To this circumstance the apostle seems evidently to allude, Heb 11:4 : By Faith Abel offered πλειονα θυσιαν, a More or Greater sacrifice; not a more excellent, (for this is no meaning of the word πλειων), which leads us to infer, according to Dr. Kennicott, that Abel, besides his minchah or gratitude offering, brought also θυσια, a victim, to be slain for his sins; and this he chose out of the first-born of his flock, which, in the order of God, was a representation of the Lamb of God that was to take away the sin of the world; and what confirms this exposition more is the observation of the apostle: God testifying τοις δωροις, of his Gifts, which certainly shows he brought more than one. According to this interpretation, Cain, the father of Deism, not acknowledging the necessity of a vicarious sacrifice, nor feeling his need of an atonement, according to the dictates of his natural religion, brought a minchah or eucharistic offering to the God of the universe. Abel, not less grateful for the produce of his fields and the increase of his flocks, brought a similar offering, and by adding a sacrifice to it paid a proper regard to the will of God as far as it had then been revealed, acknowledged himself a sinner, and thus, deprecating the Divine displeasure, showed forth the death of Christ till he came. Thus his offerings were accepted, while those of Cain were rejected; for this, as the apostle says, was done by Faith, and therefore he obtained witness that he was righteous, or a justified person, God testifying with his gifts, the thank-offering and the sin-offering, by accepting them, that faith in the promised seed was the only way in which he could accept the services and offerings of mankind. Dr. Magee, in his Discourses on the Atonement, criticises the opinion of Dr. Kennicott, and contends that there is no ground for the distinction made by the latter on the words he also brought; and shows that though the minchah in general signifies an unbloody offering, yet it is also used to express both kinds, and that the minchah in question is to be understood of the sacrifice then offered by Abel. I do not see that we gain much by this counter-criticism. See Gen 4:7.”
Source
1849
A.D.
1774–1849
“Had respect. That is, shewed his acceptance of his sacrifice (as coming from a heart full of devotion): and that we may suppose, by some visible token, such as sending fire from heaven upon his offerings. (Challoner) — The offerings of Cain are mentioned without any approbation: those of Abel are the firstlings and fat, or the very best; by which he testified, that he acknowledged God for his first beginning. Sacrifice is due to God alone, and to Him it has always been offered in the Church. We have the happiness to offer that truly eucharistic sacrifice to God, of which those of ancient times were only figures. What sacrifice can our erring brethren shew? (Worthington; Calmet)”
Source
1871
A.D.
1871
“the Lord had respect unto Abel, not unto Cain, &c.--The words, "had respect to," signify in Hebrew,--"to look at any thing with a keen earnest glance," which has been translated, "kindle into a fire," so that the divine approval of Abel's offering was shown in its being consumed by fire (see Gen 15:17; Jdg 13:20).”
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.