2 Corinthians 8:18

συνεπέμψαμεν δέ. And we are sending together with him the brother whose praise in the Gospel is through all the Churches. Certainly τὸν� means the fellow-Christian, not the actual brother of Titus. He was someone known to the Corinthians, but quite unknown to us. Barnabas, Silas, Mark, Trophimus, Sopater, Aristarchus, Secundus, and Luke are conjectures, of which Luke is perhaps the best. See on 2 Corinthians 9:4. Origen (Homilies on S. Luke) treats Luke as certainly meant. But ἐν τῷ εὐαγγελίῳ does not mean ‘in his Gospel,’ the one which he wrote; rather, in spreading the Gospel, in mission work. Nowhere in the N.T. is there mention of a written Gospel.