The interpretation timeline
2 Corinthians 8:18 Douay-Rheims

We have sent also with him the brother, whose praise is in the gospel through all the churches.

A.D. 108 – 1871 8 witnesses

Patristic

before A.D. 750
108
A.D.
c. A.D. 50–107
“It is better for a man to be silent and be [a Christian], than to talk and not to be one. "The kingdom of God is not in word, but in power." Men "believe with the heart, and confess with the mouth," the one "unto righteousness," the other "unto salvation." It is good to teach, if he who speaks also acts. For he who shall both "do and teach, the same shall be great in the kingdom." Our Lord and God, Jesus Christ, the Son of the living God, first did and then taught, as Luke testifies, "whose praise is in the Gospel through all the Churches." There is nothing which is hid from the Lord, but our very secrets are near to Him. Let us therefore do all things as those who have Him dwelling in us, that we may be His temples, and He may be in us as God. Let Christ speak in us, even as He did in Paul. Let the Holy Spirit teach us to speak the things of Christ in like manner as He did.”
Source
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“And who is this brother? Some indeed say, Luke, because of the history which he wrote, but some, Barnabas; for he calls the unwritten preaching also Gospel. And for what cause does he not mention their names; whilst he both makes Titus known by name, and praises him for his cooperation in the Gospel, (seeing that he was so useful that by reason of his absence even Paul could do nothing great and noble; for, "because I found not Titus my brother, I had no relief for my spirit,") and for his love towards them, (for, saith he, "his inward affection is more abundant towards you;") and for his zeal in this matter ("for," he saith, "of his own accord he went")? But these he neither equally commends, nor mentions by name? What then is one to say? Perhaps they did not know them; wherefore he does not dwell upon their praises because as yet they had had no experience of them, but only says so much as was sufficient for their commendation unto them (i.e. the Corinthians,) and to their escaping all evil suspicion. However, let us see on what score he eulogizes this man himself also. On what score then does he eulogize? First, praising him from his preaching; that he not only preached, but also as he ought, and with the befitting earnestness. For he said not, 'he preaches and proclaims the Gospel,' but, "whose praise is in the Gospel." And that he may not seem to flatter him, he brings not one or two or three men, but whole Churches to testify to him, saying, "through all the churches." Then he makes him respected also from the judgment of those that had chosen him. And this too is no light matter.”
Source

Scholastic

c. 1100 – 1500
1272
A.D.
Thomas Aquinas Catholic
1225–1274
“After he has treated of the giving of the collections, here he consequently treats of the ministers through whom the collections are made. And concerning this he does two things. First he names them; second he commends them to the Corinthians, at "the showing therefore which is," etc. Concerning the first he does three things. For first he names Titus; second Barnabas, at "we have also sent with him the brother," etc.; third Apollo, at "we have sent with them," etc. Concerning Titus he commends two things, namely his solicitude and the sign of his solicitude, at "for indeed the exhortation," etc. He says therefore first: I have said, above, that I asked Titus to complete this grace concerning the gathering of alms, which is incumbent upon my solicitude by the ordination of the apostles, in which matter I also found him solicitous; and therefore I give thanks to God, who gave the same solicitude, which I have, for you, to be exhorted and advanced to works of mercy, in the heart of Titus; because he too is solicitous, just as I am, that he may complete this grace in you. Heb. 6:11: we desire each one of you to show the same solicitude, etc. Rom. 12:8: he who presides, in solicitude. Now the sign of this solicitude is that when I asked him, he himself consented to my exhortation. And therefore he says: for indeed he received the exhortation. And because he pursued what I asked, whence he says: but since he was more solicitous by his own will than by my exhortation, he set out to you; who nevertheless at first refused to come on account of your sins. Rom. 12:11: in solicitude, not slothful. Consequently, when he says "but we have sent," etc., he treats of the second minister. And concerning this he does two things. First he commends him; second he adds the reason why he sends such solemn messengers, at "avoiding," etc. This brother, according to some, is Luke, or according to others Barnabas, whom indeed he commends from three things: from fame, because his praise, namely Luke's, is in the Gospel written by him throughout all the Churches, because it has been approved by the apostles. Or whose praise, namely Barnabas's, is in the Gospel preached by him throughout all the Churches, because to the Jews and to the Gentiles. Whence it is said of Barnabas, Acts 11:24, that he was a good man, full of faith and the Holy Spirit. Likewise he commends him from his companionship, because he is not only famous, but has also been appointed by the Churches of Judea as a companion of my pilgrimage, that is, of my preaching, by which, as pilgrims, we go about the world. Above ch. 5:6: as long as we are in the body, we are pilgrims from God, etc. And this is true of Luke, because he was one of the seventy-two disciples, and a companion of Paul. Of Barnabas likewise, because through the Holy Spirit it is said, Acts 13:2: separate for me Barnabas and Paul unto the work, etc. And he was made a companion in this grace, namely of the collection of alms. Or in this grace, namely of preaching, of which it is said Eph. 3:8: but to me, the least of all the saints, etc. Likewise he commends him from office, because he is a minister of the grace which is ministered by us. 1 Cor. 4:1: so let a man esteem us. Above ch. 3:6: who also has made us fit, etc. Now this grace is ministered unto the glory of the Lord, that is, that our Lord may be glorified, namely from the alms given, from the conversion of very many peoples to our preaching, because, as it is said Prov. 14:28, in the multitude of the people, etc. Likewise it is ministered, that our will may be fulfilled, because we wish this to be done. And therefore he says: and our will, destined — that is, predestined by God, who predestined from eternity that we should have such a will. Consequently, when he says "avoiding," etc., he assigns the cause why he sends such solemn messengers. And first he assigns the reason for this; second he proves it, at "we provide therefore," etc. He says therefore: the reason why we send such solemn messengers is this: that you may know that a business of this kind is present to our heart. And therefore he says "avoiding this," namely lest anyone, etc., as if to say: that we might avoid the reproach which could be cast upon me by some, either of negligence, if I did not send diligent men, or of fraud, if I did not send trustworthy ones. And these were diligent and ready and trustworthy, because they were given by the Churches and chosen through the Holy Spirit. Above ch. 6:3: giving no offense to anyone, etc. Now he says "in this abundance," namely of alms or of the conversion of the Gentiles. 1 Pet. 4:10: each one, as he has received grace, unto one another, etc. And he proves this, saying "for we provide," etc., as if to say: I rightly say "avoiding," because we provide — that is, we ought to provide — good things, that is, that our works may be good not only before God, that we may please him, but also before men, that is, that they may appear good to them. And this he does, by carefully procuring and imitating the good. Rom. 12:9: cleaving to the good, etc. Consequently, when he says "but we have sent with them our brother also," etc., he treats of the third messenger, namely of Apollo. Where he does two things. First, he commends him for his solicitude, when he says "whom," namely Apollo, "we have often proved to be solicitous for your salvation; but now much more solicitous." For, as appears above, Apollo was the first who preached at Corinth after the apostle. 1 Cor. 3:6: I planted, Apollo watered. But this man, disturbed by their sin, withdrew, and set aside the solicitude which he had before had for them. But now, having heard of their conversion, he became more solicitous for their salvation than he had been before. Eph. 4:3: solicitous to keep the unity of the spirit, etc. Rom. 12:8: he who presides, in solicitude, etc. Second, he adds the cause of the solicitude which he took up, because Apollo trusted concerning you from those things which Titus said about you, commending you. Whence he says "with much confidence in you," whether on account of Titus who is my companion, and because he willingly came into the fellowship of Titus and Luke or Barnabas, and because he was induced to this by the apostles of the Churches which are in Judea. And therefore he says "or our brethren," the apostles of the Churches of Judea, namely they induced him to have solicitude for you. Which Churches indeed are "of the glory of Christ," that is, unto the glory of Christ. Consequently, when he says "the showing therefore which is," etc., he commends these messengers to the Corinthians, saying: because we have sent such men to you, therefore "the showing," etc., that is, show by deed, that you have charity toward them, and that I have truly commended you, and that I have truly gloried concerning you in the face of the Churches, to which I have come and to which I have preached. Or "in the face of all the Churches," because what you do to them will become known to all the Churches.”

Reformation

c. 1500 – 1650
1637
A.D.
1567–1637
“And we have sent with him the brother whose praise is in the Gospel Barnabas, whose praise is in the preaching of the Gospel. He was ordained as S. Paul’s companion (Acts xiii. 3) (Theodoret, Chrysostom, CEcumenius); but since Barnabas and Paul were now separated, and Silas had taken S. Barnabas’ place at S. Paul’s side (Acts xv. 40), it is better with Baronius to take the reference as being to Silas, or, with Anselm and Jerome, to Luke. S. Paul calls him brother , not Apostle, and this applies better to S. Luke, who wrote a Gospel, and was the inseparable companion of S. Paul. S. Ignatius, writing to the Ephesians, assigned this eulogy to Luke in the words: “As Luke testifies, whose praise is in the Gospel.””
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“And not that only, but who was also chosen of the churches,.... Not only famous for preaching the Gospel, but he was also appointed by the joint suffrages of the churches, which were made by the lifting up or stretching out of the hand, as the word here used signifies; this brother was not chosen to this service by a few private persons, or by a single church only, but by several churches; which does not refer to the churches at Jerusalem and Antioch, as if the apostles were appointed, and others were appointed by these churches to travel with them, in order to collect money for the poor saints at Jerusalem; of which no mention is any where made, only of their being sent out by them to preach the Gospel. James, Cephas, and John indeed, when they gave to Paul and Barnabas the right hand of fellowship, that they might go to the Heathen, desired them to "remember the poor"; Gal 2:9 but these were not the churches. The church at Antioch did collect for the brethren in Judea, at the time of the famine among them, and sent their bounty by the hands of Barnabas and Saul, which seems to be the case here. This brother was chosen by the churches who collected, and not by the churches in Judea, for whom the collections were made; for it was usual, and what was right and proper, that the churches chose whom they thought fit to carry their liberality to Jerusalem; see Co1 16:3. Now this brother had the honour to be chosen by these churches, to travel, says the apostle, with us, with this grace; bounty or beneficence of the churches, what they had freely and liberally contributed for the supply of the poor, from a principle of grace, and by the assistance of it; which is administered by us; not given by the apostles, but collected by them; or what was procured by their means, in the several churches to whom they had moved it, and by proper arguments had excited them to it, with which they cheerfully complied: and this was done on a two fold account, both to the glory of the same Lord: Jesus Christ, who is the one Lord over all; the same Lord of the apostles, and the church at Corinth; the same Lord of the Corinthians, and the Macedonian and other churches; and the same Lord of the poor saints at Jerusalem, and the rich members of the several churches that contributed to them: and also to the declaration of your ready mind; or to stir up their ready mind to increase it and promote it in them, as well to make it manifest, and that it might appear to others, how readily and freely they came into this service; so that the apostle's concern in this administration was not from any sinister and selfish ends; no, nor so much for the relief of the poor, though this was greatly designed, as for the glory of Christ, and the honour of his churches.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“The brother, whose praise is in the Gospel - Who this brother was we cannot tell; some suppose it was St. Luke, who wrote a gospel, and who was the companion of St. Paul in several of his travels; others think it was Silas; others, Barnabas; others, Mark; and others, Apollos. Neither ancients nor moderns agree in either; but Luke, John, and Mark, seem to have the most probable opinions in their favor. Whoever the person was he was sufficiently known to the Corinthians, as we learn by what the apostle says of him in this place.”
Source
1849
A.D.
1774–1849
“Brother, whose praise is in the gospel, through all the Churches. [2] It may either signify in writing or in preaching the gospel, so that though St. Jerome expound this of St. Luke, who wrote his gospel, (but probably not till after this time) yet St. Chrysostom rather understands it of Barnabas, by the words that follow, who was ordained by the Churches companion of our travels. Others also guess it might be Silas or Silvanus. Who the third brother was, is also uncertain. (Witham) — Commentators very in their opinions upon the person here mentioned. St. Chrysostom and Theo. are of opinion, that this person is St. Luke or Barnabas; St. Jerome also thinks that it must be St. Luke the evangelist.”
Source
1871
A.D.
1871
“the brother, whose praise is in the gospel--whose praise is known in connection with the Gospel: Luke may be meant; not that "the Gospel" here refers to his written Gospel; but the language implies some one well known throughout the churches, and at that time with Paul, as Luke then was (Act 20:6). Not a Macedonian, as appears from Co2 9:4. Of all Paul's "companions in travel" (Co2 8:19; Act 19:29), Luke was the most prominent, having been his companion in preaching the Gospel at his first entrance into Europe (Act 16:10). The fact that the person here referred to was "chosen of the churches" as their trustee to travel with Paul in conveying the contribution to Jerusalem, implies that he had resided among them some time before: this is true of Luke, who after parting from Paul at Philippi (as he marks by the change from "we" to "they," Act 16:11) six years before, is now again found in his company in Macedonia. In the interim he had probably become so well known that "his praise was throughout all the churches." Compare Co2 12:18; Plm 1:24. He who is faithful in the Gospel will be faithful also in matters of inferior importance [BENGEL].”
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.