The interpretation timeline
Mark 1:2 Douay-Rheims

As it is written in Isaias the prophet: Behold I send my angel before thy face, who shall prepare the way before thee.

A.D. 420 – 1871 10 witnesses 17 excerpts

Patristic

before A.D. 750
420
A.D.
Jerome Patristic
c. A.D. 347–420
“(ad Pammach. Epist. 57) But this is not written in Isaiah, but in Malachi, the last of the twelve prophets.”
“By Malachi, therefore, the voice Πνεύμκτος Ἅγιου of the Holy Spirit resounds to the Father concerning the Son, who is the countenance of the Father by which He has been known.”
735
A.D.
Bede the Venerable Patristic
c. A.D. 672–735
“(ubi sup.) Being about to write his Gospel, Mark rightly puts first the testimonies of the Prophets, that he might notify to all, that what he should write was to be received without scruple of doubt, in that he shewed that these things were beforehand foretold by the Prophets. At once, by one and the same beginning of his Gospel, he prepared the Jews, who had received the Law and the Prophets, for receiving the grace of the Gospel, and those sacraments, which their own prophecies had foretold; and he also calls upon the Gentiles, who came to the Lord by publishing of the Gospel, to receive and venerate the authority of the Law and the Prophets; whence he says, As it is written in the prophet Isaiah, Behold, &c.”
Source
“(ubi sup.) Or otherwise, we must understand, that, although these words are not found in Isaiah, still the sense of them is found in many other places, and most clearly in this which he has subjoined, The voice of one crying in the wilderness. For that which Malachi has called, the angel to be sent before the face of the Lord, to prepare His way, is the same thing as Isaiah has said is to be heard, the voice of one crying in the wilderness, saying, Prepare ye the way of the Lord. But in each sentence alike, the way of the Lord to be prepared is proclaimed. It may be, too, that Isaiah occurred to the mind of Mark, in writing his Gospel, instead of Malachi, as often happens; which he would, however, without doubt correct, at least when reminded by other persons, who might read his work whilst he was yet in the flesh; unless he thought, that, since his memory was then ruled by the Holy Spirit, it was not without a purpose, that the name of one prophet had occurred to him instead of another. For thus whatsoever things the Holy Spirit spoke by the prophets, are implied each to have belonged to all, and all to each.”
Source
“(ubi sup.) But John is called an angel not by community of nature, according to the heresy of Origena, but by the dignity of his office; for angel in Greek is in Latin, nuntius, (messenger,) by which name that man is rightly called, who was sent by God, that he might bear witness of the light, and announce to the world the Lord, coming in the flesh: since it is evident that all who are priests may by their office of preaching the Gospel be called angels, as the prophet Malachi says, The lips of the priest keep knowledge, and they seek the law at his mouth, because he is the Angel of the Lord of hosts. (Mal. 2:7)”
Source
“(ubi sup.) But as John might be called an angel, because he went before the face of the Lord by his preaching, so he might also be rightly called a voice, because, by his sound, he preceded the Word of the Lord. Wherefore there follows, The voice of one crying, &c. For it is an acknowledged thing that the Only-Begotten Son is called the Word of the Father, and even we, from having uttered words ourselves, know that the voice sounds first, in order that the word may afterwards be heard.”
Source

Scholastic

c. 1100 – 1500
1107
A.D.
c. 1055–1107
“The Forerunner of Christ, therefore, is called an angel, on account of his angelic life and lofty reverence. Again, where he says, Before thy face, it is as if he said, Thy messenger is near thee: whence is shewn the intimate connection of the Forerunner with Christ; for those walk next to kings, who are their greatest friends. There follows, Who will prepare thy way before thee. For by baptism he prepared the minds of the Jews to receive Christ.”
Source
“Or, the way is the New Testament, and the paths are the Old, because it is a trodden path. For it was necessary to be prepared for the way, that is, for the New Testament; but it was right that the paths of the Old Testament should be straightened.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“As it is written in the prophets,.... Malachi and Isaiah; for passages out of both follow; though the Vulgate Latin, Syriac, and Persic versions read, "as it is written in the prophet Isaias"; and so it is in some Greek copies: but the former seems to be the better reading, since two prophets are cited, and Isaiah is the last; to which agree the Arabic and Ethiopic versions, and the greater number of Greek copies. The following citations are made to show, that according to the writings of the Old Testament, John the Baptist was to be the harbinger of Christ, to come before him, and prepare his way; and also the propriety of the method the evangelist takes, in beginning his Gospel with the account of John's ministry and baptism: the first testimony stands in Mal 3:1, and the words are the words of the Father to the son, concerning John, pointing out his character and his work: behold, I send my messenger before thy face, which shall prepare thy way before thee. John the Baptist is here called a messenger, and the message he was sent and came with, was of the greatest moment and importance, and required the closest attention to it; wherefore this passage is introduced with a "behold!" signifying that something momentous, and what should be strictly regarded, was about to be delivered: and indeed, the work of this messenger was no other, than to declare that the long expected Messiah was born; that he would quickly make his public appearance in Israel; that the kingdom of heaven, or the kingdom of the Messiah, was at hand; and that it became the Jews to repent of their sins, and believe in Christ: he is called the messenger of God, "my messenger"; because he was sent, and sanctified by him; he was called unto, and qualified for his work by him; see Joh 1:6, his father Zechariah says, he should be called the prophet of the Highest, Luk 1:76. The reason of his being called the messenger of God, may be observed in the text itself, "behold, I send": the words in Malachi are by us rendered, "behold, I will send", Mal 3:1, because this was at the time of the prophet's writing a thing future, but in the times of the evangelist a thing done: and indeed, it is a more literal version of the Hebrew text, to render it "I send", or "am sending"; and it is so expressed, to denote the certainty of it, and because in a little time it would be done: the words "before thy face", are not in the original text of Malachi, nor in the Septuagint version, but are inserted by the evangelist; who might do it with authority, since Christ had done it before him, Mat 11:10, and which, as Surenhusius (c) observes, is for the greater elucidation of the matter. The prophet does not say before whom he should be sent, though it is implied in the next clause, but here it is expressed: besides, this messenger had now appeared before the face of Christ, had prepared his way in the wilderness, and had baptized him in Jordan; all which is designed in the following words, "which shall prepare thy way before thee", by his doctrine and baptism: in the text in Malachi it is, "before me", Mal 3:1; which has made it a difficulty with the interpreters, whether the words in the prophet, are the words of Christ concerning himself, or of his Father concerning him. But sending this messenger before Christ, may be called by the Father sending him before himself, and to prepare the way before him; because Christ is the brightness of his glory, and the express image of his person, and is the angel of his presence, or face; besides, Jehovah the Father was greatly concerned, and the glory of his perfections, in the work the Messiah was to do, whose way John came to prepare. That the prophecy in Malachi here cited, is a prophecy of the Messiah, is owned by several Jewish writers (d); who expressly say, that those words which follow, "the Lord whom ye seek", are to be understood of the king Messiah: and though they are divided among themselves, who should be meant by this messenger; see Gill on Mat 11:10, yet some of them are of opinion, that Elias is intended, even Abarbinel himself: for though in his commentary he interprets the words of the prophet Malachi himself, yet elsewhere (e) he allows Elias may be intended: indeed he, and so most that go this way, mean Elijah the prophet, the Tishbite; who they suppose will come in person, before the Messiah appears: yet not he, but one in his Spirit and power is designed; and is no: other than John the Baptist, in whom the passage has had its full accomplishment. (c) Biblos Katallages, p. 229. (d) Kimchi & Ben Melech in Mal. iii. 1. Abarbinel, Mashmia Jeshua, fol. 76. 4. (e) Abarbinel, Mashmia Jeshua, fol. 76. 4.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“As it is written in the prophets - Rather, As it is written by Isaiah the prophet. I think this reading should be adopted, instead of that in the common text. It is the reading of the Codex Bezae, Vatican, and several other MSS. of great repute. It is found also in the Syriac, Persic, Coptic, Armenian, Gothic, Vulgate, and Itala versions, and in several of the fathers. As this prophecy is found both in Isaiah and Malachi, probably the reading was changed to τοις προφηταις, the prophets, that it might comprehend both. In one of Asseman's Syriac copies, both Isaiah and Malachi are mentioned. See all the authorities in Griesbach, 2d edit.; and see the parallel place in Matthew, Mat 3:3, where the Prophet Isaiah is mentioned, which seems fully to establish the authority of this reading.”
Source
1849
A.D.
1774–1849
“In Isaias, the prophet. That in the ancient copies was read Isaias, and not Malachias, is confirmed by the Syriac version, and also by St. Irenĉus, Origen, St. Jerome, &c. It is also proved from an objection of Porphyrius, who says, St. Mark mistook Isaias for Malachias. In the ordinary Greek copies at present, we read in the prophets, not naming either Isaias or Malachias. The words seem taken partly out of one, and partly out of the other. These words, behold I send my angel before thy face, who shall prepare thy way before thee, are found Malachias iii. ver. 1. And the following words, a voice of one crying in the desert: prepare ye the way of the Lord, make straight his paths, are in Isaias, chap. xl, ver. 3. (Witham) — In the beginning of his gospel, St. Mark alleges the authority of the prophets, that he might induce every one, both Jew and Gentile, to receive with willingness what he here relates, as the authority of the prophets so highly respected was very great. St. John [the Baptist] is here styled an angel, on account of his angelic life, and extraordinary sanctity; but what is meant by, who shall prepare thy way, is, that St. John is to prepare the minds of the Jews, by his baptism and preaching, to receive their Messias. (Theophylactus) See in Matthew xi. 10.”
Source
1871
A.D.
1871
“As it is written in the prophets, Behold, I send my messenger before thy face, which shall prepare thy way before thee-- (Mal 3:1; Isa 40:3).”

Undated

date unknown
date
unknown
“(Vict. Ant. c. Cat. in Marc.) But it may be said that it is a mistake of the writer. Otherwise it may be said, that he has compressed into one, two prophecies delivered in different places by two prophets; for in the prophet Isaiah it is written after the story of Hezekiah, The voice of one crying in the wilderness; but in Malachi, Behold, I send mine angel. The Evangelist therefore, taking parts of two prophecies, has put them down as spoken by Isaiah, and refers them here to one passage, without mentioning, however, by whom it is said, Behold, I send mine angel.”
Source
date
unknown
“(Quæst. nov. et vet. Test. lvii.) For knowing that all things are to be referred to their author, he has brought these sayings back to Isaiah, who was the first to intimate the sense. Lastly, after the words of Malachi, he immediately subjoins, The voice of one crying in the wilderness, in order to connect the words of each prophet, belonging as they do to one meaning, under the person of the elder prophet.”
Source
date
unknown
“Or, the way of the Lord, by which He comes into men, is penitence, by which God comes down to us, and we mount up to Him. And for this reason the beginning of John’s preaching was, Repent ye.”
“But it is called the voice of one crying, for we are wont to use a cry to deaf persons, and to those afar off, or when we are indignant, all which things we know applied to the Jews; for salvation is far from the wicked, and they stopped their ears like deaf adders, and deserved to hear indignation, and wrath, and tribulation from Christ.”
Source
date
unknown
“(Vict. Ant. e. Cat. in Marc.) But the prophecy, by saying, In the wilderness, plainly shews that the divine teaching was not in Jerusalem, but in the wilderness, which was fulfilled to the letter by John the Baptist in the wilderness of Jordan, preaching the healthful appearing of the Word of God. (non occ.). The word of prophecy also shews, that besides the wilderness, which was pointed out by Moses, where he made paths, there was another wilderness, in which it proclaimed that the salvation of Christ was present.”
Source
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.