Volume 6, Book 60, Number 202:
Narrated Ibn Abbas:
When the Prophet arrived at Medina, the Jews were observing the fast on ‘Ashura’ (10th of
Muharram) and they said, “This is the day when Moses became victorious over Pharaoh,” On that,
the Prophet said to his companions, “You (Muslims) have more right to celebrate Moses’ victory than
they have, so observe the fast on this day.”