2 Corinthians 8:18

And we have sent together with him the brother whose praise in the gospel is spread through all the churches.

Adam Clarke capitalized the word "Gospel" in this verse, making it bear the meaning that the brother Paul sent with Titus was the author of one of the canonical Gospels. Scholars, of course, generally dispute such a meaning; but it positively must be allowed as possible. If this brother was Luke (as some of the oldest traditions affirm), it would mean that Luke had been concerned with compiling a gospel long before the date usually assigned to the third Gospel (which is by no means an impossibility). However, whether or not this was Luke (and no one really knows), one thing is positively evident: there was a written gospel even at this early date, a fact confirmed by Luke's introduction (2 Corinthians 1:1-5).

Through all the churches ... The brother mentioned was known "through all" the churches. It is amazing that the same scholars who pin so much faith in the absolute superlatives of 2 Corinthians 7:13-15 are here very quick to affirm that "Here, ALL may refer only to the churches sharing in the collection"![24] This, however, is arbitrary. Certainly, some "gospel" was read by every church on earth at that time; and it must be allowed that the author of whatever gospel that was is the man Paul referred to here. The personal view of this writer is that this is a reference to the evangelist Luke and to the gospel that bears his name. None of the objections to this view is convincing. For full discussion of the subject, see the Commentary of Philip E. Hughes on this epistle, pp. 312-316.