A.T. Robertson Commentary Acts 15:27

"We have sent therefore Judas and Silas, who themselves also shall tell you the same things by word of mouth." — Acts 15:27 (ASV)

Who themselves also shall tell you the same things by word of mouth (κα αυτους δια λογου απαγγελλοντας τα αυτα). Literally, "they themselves also by speech announcing the same things." The present participle, as here, sometimes is used like the future to express purpose as in 3:26 ευλογουντα after απεστειλεν and so here απαγγελλοντας after απεσταλκαμεν (Robertson, Grammar, p. 1128). Judas and Silas are specifically endorsed (perfect active indicative of αποστελλω) as bearers of the epistle who will also verbally confirm the contents of the letter.