四分律比丘含注戒本 2.185

2.185

佛在舍衛。大愛道尼來請教授，佛令差往，僧次般陀往彼說法，六群次往，向說世論。愛道白佛，便羯磨差而制戒也。

(The Buddha was in Śrāvastī. Mahāprajāpatī Gautamī came to request instruction. The Buddha ordered that someone be appointed to go. In the Saṃgha's turn, Panthaka went there to preach the Dharma. Next, the group-of-six went, and spoke worldly discourse to them. Mahāprajāpatī reported this to the Buddha, who thereupon instituted the appointment through karman and formulated the precept.)