Apostolic Constitutions, VIII. i. § 5:  “And after the reading of the Law and the Prophets, and our Epistles, and Acts, and Gospels, let him that is ordained…speak to the people the word of exhortation, and when he has ended his discourse of doctrine, all standing up, let the Deacon ascend upon some high seat, and proclaim, Let none of the hearers, let none of the unbelievers stay:  and silence being made, let him say, Ye Catechumens, pray, and let all the Faithful pray for them.”