The Council of Nicaea
Concerning catechumens who have lapsed, the holy and great Synod has decreed that, after they have passed three years only as hearers, they shall pray with the catechumens.
Source details
A.D. 325 · Canon 14 (325)
Checked word-for-word against Nicene and Post-Nicene Fathers, Series 2, Vol. 14 · 2026-07-26