2 Corinthians 8:18

“And we have sent with him the brother, etc..] The Syriac and Ethiopic versions read, “our brother”; and one of Stephens's copies, “your brother”: who this brother was, is not certain; some think it was Luke the evangelist, the companion of the apostle in his travels: whose praise is in the Gospel, throughout all the churches; being known and highly commended by all the churches, for the Gospel he wrote; but it is not certain that Luke as yet had wrote his Gospel; and much less that it was so much known at present among the churches; and besides, this brother's praise seems to be on account of his preaching the Gospel, and not writing one: others think Barnabas is intended, who was chosen and…”

“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…”

“And we have sent with him the brother - It has been generally supposed that this anonymous brother was Luke. Some have supposed however that it was Mark, others that it was Silas or Barnabas. It is impossible to determine with certainty who it was; nor is it material to know. Whoever it was, it was some one well known, in whom the church at Corinth could have entire confidence. It is remarkable that though Paul mentions him again 2 Corinthians 12:18, he does it also in the same manner, without specifying his name. The only circumstances that can throw any light on this are: (1) That Luke was the companion and intimate friend of Paul, and attended him in his travels. From Acts 16:10-11, where…”

“We - I and Timothy. The brother - The ancients generally supposed this was St. Luke. Whose praise - For faithfully dispensing the gospel, is through all the churches. 2 Corinthians 8:19”

“8:18-24 Two other Christian men would travel with Titus to Corinth in order to guard against any criticism over the handling of the relief funds that they collected (8:20-21). Titus and his companions would ensure that the money was properly handled. The identity of the two companions is unknown.”

“the brother: This is generally supposed to have been Said. Luke, "whose praise was in all the churches," on account of the gospel which he had written, and for many zealous services in its cause. Co2 8:19, Co2 8:22, Co2 8:23, Co2 12:18 throughout: Rom 16:4 2 Corinthians 8:19”