四分律比丘含注戒本 3.438

3.438

佛在瞻波國。白月十五日僧說戒時，佛在眾坐，默不說戒。初夜已過，阿難請說，佛言：「欲令如來於不淨眾中說戒者，無此理也。」中夜、後夜請，答亦爾。時大目連即以天眼觀犯戒者去佛不遠，內懷腐爛，外現完淨，即手牽出，來白佛言：「眾已清淨，應得說戒。」佛言：「自今已後不應為。取自言治。」因制此戒。

The Buddha was in the country of Campā. On the fifteenth day of the bright fortnight, at the time of the Saṃgha's recitation of the precepts, the Buddha sat in the assembly and remained silent without reciting the precepts. When the first watch of the night had passed, Ānanda requested him to recite them. The Buddha said, “To expect the Tathāgata to recite the precepts amidst an impure assembly—there is no such possibility.” When requested during the middle watch and the last watch, the reply was the same. At that time, Mahāmaudgalyāyana surveyed with the divine eye and saw a precept-breaker not far from the Buddha, inwardly harboring rot while outwardly appearing complete and pure. He immediately took him by the hand, led him out, and came to report to the Buddha, saying, “The assembly is now pure; the precepts may be recited.” The Buddha said, “From now on, this must not be done [by me]. One must adopt settlement upon voluntary confession.” On account of this, he formulated this rule.