四分律比丘含注戒本 2.3

2.3

佛在釋翅瘦。釋子象力善能談論，與外道論議不如時，便反前語；若僧中問，復違反語。梵志譏無正法，比丘舉過白佛。因制此戒。

The Buddha was in Śākyavartin. The Śākya Hastikāśyapa was adept at debate; when he was getting the worst of a debate with non-Buddhists, he went back on his previous words; if questioned in the Saṃgha, he also contradicted his words. The brahmins ridiculed them, saying there was no True Dharma, and bhikṣus reported the fault to the Buddha. On this occasion, he laid down this precept.