諸經要集 14.91

14.91

又興起行經云。釋迦過去以惡語道迦葉禿頭沙門何有佛道。故今六年。受日食一麻一米大豆。苦行如是。

Furthermore, the Xingqixing jing says: In the past, Śākyamuni spoke evil words against Kāśyapa, saying, 'Where could a bald-headed śramaṇa have the Buddha-way?' Therefore, for six years in this life, he endured ascetic practices like this, eating one hemp seed and one grain of rice or large bean a day.