增壹阿含經 24.5.p152

24.5.p152

The eternal rule of Buddhas is that if they say, “Welcome, monk!” then one becomes an ascetic. The Bhagavān told Kāśyapa, “Welcome, monk! This teaching is subtle. Cultivate the religious life well!” The robes that Kāśyapa and the 500 disciples were wearing all turned into reddish-brown robes, and their hair fell out on its own. They looked like they shaved their heads, and it lasted for seven days. Kāśyapa then took his implements for studying magic and incantations and tossed them all into the river.