Is the Prophet (peace be upon him) authentically reported to have observed Sawm for the first ten days of Dhul-Hijjah?
It is not authentically reported that the Prophet (peace be upon him) observed Sawm the first ten days of Dhul-Hijjah - better described as the nine days preceding `Eid-ul-Adha (the Festival of the Sacrifice). However, he (peace be upon him) urged people to do good deeds during these days. The Prophet (peace be upon him) is authentically reported to have stated:
"No good deed performed on other days are superior to those performed during these (first ten days of Dhul-Hijjah)." (Part No. 10; Page No. 400) Then some companions of the Prophet asked, "Not even Jihad?" He replied, "Not even Jihad, except that of a man who does it by putting himself and his property in danger (for Allah's sake) and does not return with any of those things."
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.