1 But that this Luke was inseparable from Paul, and his fellow-labourer in the Gospel, he himself clearly evinces, not as a matter of boasting, but as bound to do so by the truth itself. For he says that when Barnabas, and John who was called Mark, had parted company from Paul, and sailed to Cyprus, “we came to Troas;” and when Paul had beheld in a dream a man of Macedonia, saying, “Come into Macedonia, Paul, and help us,” “immediately,” he says, “we endeavoured to go into Macedonia, understanding that the Lord had called us to preach the Gospel unto them. Therefore, sailing from Troas, we directed our ship's course towards Samothracia.” And then he carefully indicates all the rest of their journey as far as Philippi, and how they delivered their first address: “for, sitting down,” he says, “we spoke unto the women who had assembled;” and certain believed, even a great many. And again does he say, “But we sailed from Philippi after the days of unleavened bread, and came to Troas, where we abode seven days.” And all the remaining [details] of his course with Paul he recounts, indicating with all diligence both places, and cities, and number of days, until they went up to Jerusalem; and what befell Paul there, how he was sent to Rome in bonds; the name of the centurion who took him in charge; and the signs of the ships, and how they made shipwreck; and the island upon which they escaped, and how they received kindness there, Paul healing the chief man of that island; and how they sailed from thence to Puteoli, and from that arrived at Rome; and for what period they sojourned at Rome. As Luke was present at all these occurrences, he carefully noted them down in writing, so that he cannot be convicted of falsehood or boastfulness, because all these [particulars] proved both that he was senior to all those who now teach otherwise, and that he was not ignorant of the truth. That he was not merely a follower, but also a fellow-labourer of the apostles, but especially of Paul, Paul has himself declared also in the Epistles, saying: “Demas has forsaken me,... and is departed unto Thessalonica; Crescens to Galatia, Titus to Dalmatia. Only Luke is with me.” From this he shows that he was always attached to and inseparable from him. And again he says, in the Epistle to the Colossians: “Luke, the beloved physician, greets you.” But surely if Luke, who always preached in company with Paul, and is called by him “the beloved,” and with him performed the work of an evangelist, and was entrusted to hand down to us a Gospel, learned nothing different from him (Paul), as has been pointed out from his words, how can these men, who were never attached to Paul, boast that they have learned hidden and unspeakable mysteries?
2. But that Paul taught with simplicity what he knew, not only to those who were [employed] with him, but to those that heard him, he does himself make manifest. For when the bishops and presbyters who came from Ephesus and the other cities adjoining had assembled in Miletus, since he was himself hastening to Jerusalem to observe Pentecost, after testifying many things to them, and declaring what must happen to him at Jerusalem, he added: “I know that you shall see my face no more. Therefore I take you to record this day, that I am pure from the blood of all. For I have not shunned to declare unto you all the counsel of God. Take heed, therefore, both to yourselves, and to all the flock over which the Holy Ghost has placed you as bishops, to rule the Church of the Lord, which He has acquired for Himself through His own blood.” Then, referring to the evil teachers who should arise, he said: “I know that after my departure shall grievous wolves come to you, not sparing the flock. Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them.” “I have not shunned,” he says, “to declare unto you all the counsel of God.” Thus did the apostles simply, and without respect of persons, deliver to all what they had themselves learned from the Lord. Thus also does Luke, without respect of persons, deliver to us what he had learned from them, as he has himself testified, saying, “Even as they delivered them unto us, who from the beginning were eye-witnesses and ministers of the Word.”
3. Now if any man set Luke aside, as one who did not know the truth, he will, [by so acting,] manifestly reject that Gospel of which he claims to be a disciple. For through him we have become acquainted with very many and important parts of the Gospel; for instance, the generation of John, the history of Zacharias, the coming of the angel to Mary, the exclamation of Elisabeth, the descent of the angels to the shepherds, the words spoken by them, the testimony of Anna and of Simeon with regard to Christ, and that twelve years of age He was left behind at Jerusalem; also the baptism of John, the number of the Lord's years when He was baptized, and that this occurred in the fifteenth year of Tiberius Cæsar. And in His office of teacher this is what He has said to the rich: “Woe unto you that are rich, for you have received your consolation;” and “Woe unto you that are full, for you shall hunger; and you who laugh now, for you shall weep;” and, “Woe unto you when all men shall speak well of you: for so did your fathers to the false prophets.” All things of the following kind we have known through Luke alone (and numerous actions of the Lord we have learned through him, which also all [the Evangelists] notice): the multitude of fishes which Peter's companions enclosed, when at the Lord's command they cast the nets; the woman who had suffered for eighteen years, and was healed on the Sabbath day; the man who had the dropsy, whom the Lord made whole on the Sabbath, and how He did defend Himself for having performed an act of healing on that day; how He taught His disciples not to aspire to the uppermost rooms; how we should invite the poor and feeble, who cannot recompense us; the man who knocked during the night to obtain loaves, and did obtain them, because of the urgency of his importunity; how, when [our Lord] was sitting at meat with a Pharisee, a woman that was a sinner kissed His feet, and anointed them with ointment, with what the Lord said to Simon on her behalf concerning the two debtors; also about the parable of that rich man who stored up the goods which had accrued to him, to whom it was also said, “In this night they shall demand your soul from you; whose then shall those things be which you have prepared?” and similar to this, that of the rich man, who was clothed in purple and who fared sumptuously, and the indigent Lazarus; also the answer which He gave to His disciples when they said, “Increase our faith;” also His conversation with Zaccheus the publican; also about the Pharisee and the publican, who were praying in the temple at the same time; also the ten lepers, whom He cleansed in the way simultaneously; also how He ordered the lame and the blind to be gathered to the wedding from the lanes and streets; also the parable of the judge who feared not God, whom the widow's importunity led to avenge her cause; and about the fig-tree in the vineyard which produced no fruit. There are also many other particulars to be found mentioned by Luke alone, which are made use of by both Marcion and Valentinus. And besides all these, [he records] what [Christ] said to His disciples in the way, after the resurrection, and how they recognised Him in the breaking of bread.
Source: Adversus haereses (New Advent)