Сахих Муслима 1125b

This hadith is narrated on the authority of Hisham with the same chain of transmitters, but he made no mention in the first part of the hadith that the Messenger of Allah (ﷺ) used to observe fast, and said about the second part that he abandoned the (fast) of Ashura, and he who wished observed the fast and who wished otherwise abandoned it, and he did not hold it as the words of the Messenger of Allah (ﷺ) as mentioned in the narration transmitted by Jarir