Musannaf Ibn Abi Shayba 33:582

Yahya ibn Abi Bukayr narrated to us, from Shu'bah, from 'Abd al-Malik ibn Maysarah, who said: I heard Ziyad narrating from Rib'i ibn Hirash, from Hudhayfah, that he said: "There was a day, had death come to me [then], I would not have doubted. But today, I have mixed with things, and I do not know upon what [state] I am regarding them." And he advised Abu Mas'ud, saying: "Hold fast to what you know, and beware of inconsistency (changing colors) in the religion of Allah."