The Sixth Ecumenical Council.
Canon III. Of Continence.…
Aurelius the bishop said: When at the past council the matter on continency and chastity was considered, those three grades, which by a sort of bond are joined to chastity by their consecration, to wit bishops, presbyters, and deacons, so it seemed that it was becoming that the sacred rulers and priests of God as well as the Levites, or those who served at the divine sacraments, should be continent altogether, by which they would be able with singleness of heart to ask what they sought from the Lord: so that what the apostles taught and antiquity kept, that we might also keep.
Ancient Epitome of Canon III.
Let a bishop, a presbyter, and a deacon be chaste and continent.
This canon is taken from Canon ij., of Carthage 387 or 390.