From Sahih Muslim (Hadith 2962):
Abdullah b. Shaqiq reported that 'Uthman (Allah be pleased with him) used to forbid Tamattu', whereas 'Ali (Allah be pleased with him) ordered to do it. 'Uthman said a word to 'Ali, but 'Ali said:You know that we used to perform Tamattu' with the Messenger of Allah (ﷺ), whereupon he said: It is right, but we entertained fear
Reference: Muslim 2962