四分律比丘含注戒本 3.325

3.325

佛在舍衛。六群著革屣入佛塔中，有慚比丘以過白佛，因訶制戒。

The Buddha was in Śrāvastī. The group of six entered a Buddha stūpa wearing leather sandals. Bhikṣus with a sense of shame reported the fault to the Buddha, who thereupon rebuked them and formulated the precept.