Ibn Abbas (RA) (Allah be pleased with both of them) reported that when Allah's Messenger ( صلی اللہ علیہ وسلم ) came to Madinah, he found the Jews observing the fast on the day of Ashura. They (the Jews) were asked about it and they said: It is the day on which Allah granted victory to Moses (ؑ) and (his people) Bani Isra'il over the Pharaoh and we observe fast out of gratitude to Him. Upon this the Apostle of Allah ( صلی اللہ علیہ وسلم ) said: We have a closer connection with Moses (ؑ) than you have, and he commanded to observe fast on this day.

This hadith has been narrated by Ibn Bishr with the same chain of transmitters (but with a slight variation) that he (the Holy Prophet) inquired of them (Jews) about it (fasting on the day of 'Ashura).

Ibn'Abbas (Allah be pleased with both of them) reported that the Messenger of Allah ( صلی اللہ علیہ وسلم ) arrived in Madinah and found the Jews observing fast on the day of 'Ashura. The Messenger of Allah ( صلی اللہ علیہ وسلم ) said to them: What is the (significance) of this day that you observe fast on it? They said: It is the day of great (significance) when Allah delivered Moses (ؑ) and his people, and drowned the Pharaoh and his people, and Moses (ؑ) observed fast out of gratitude and we also observe it. Upon this the Messenger of Allah ( صلی اللہ علیہ وسلم ) said: We have more right, and we have a closer connection with Moses (ؑ) than you have; so Allah's Messenger ( صلی اللہ علیہ وسلم ) observed fast (on the day of 'Ashura), and gave orders that it should be observed.

This hadith has been narrated on the authority of Ayyub with the same chain of transmitters.