四分律比丘含注戒本 1.93

1.93

佛在毘舍離，為諸比丘說不淨觀。彼習定已，厭患身命，歎死，勸死。難提比丘受雇殺人，居士驚怖。佛知此事，便說禪法。比丘修習，並證上果。因訶上過，而制此戒。

The Buddha was in Vaiśālī, expounding the contemplation of impurity for the bhikṣus. Having practiced this concentration, they grew disgusted with their bodies and lives, praising death and encouraging death. The bhikṣu Nandi was hired to kill people, terrifying the householders. The Buddha, learning of this matter, then taught the methods of dhyāna. The bhikṣus cultivated them and all realized the higher fruits. Because of rebuking the aforementioned fault, he instituted this precept.