مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3189
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from 'Abdullah bin 'Umair, a freed slave of Ibn 'Abbas, from Ibn 'Abbas (رضي الله عنه) that he said: The Messenger of Allah (ﷺ) said: "If I am still alive next year, I shall certainly fast on the ninth day.”
Musnad Ahmad 3213Its isnad is qawi]