Musnad Ahmad 3998

It was narrated that 'Abdur-Rahman bin Yazeed said: al-Ash'ath bin Qais entered upon 'Abdullah on the day of 'Ashoora' and he was eating lunch. He said: O Abu Muhammad, come and eat lunch. He said: Is it not the day of ‘Ashdora'? He said: Do you know what the day of ‘Ashoora' is? Rather the Messenger of Allah (ﷺ) used to fast it before (the command to fast) Ramadan was revealed; when (the command to fast) Ramadan was revealed, it was given up.