First Ten Days of Dhul-Hijjah (Hadith No. 784)
Hadith no. 783 is a repeat. Read it here.
Volume 2, Book 15, Number 784:
Narrated Ibn Abbas:
The Prophet said, “No good deeds done on other days are superior to those done on these (first ten days of Dhul Hijja).” Then some companions of the Prophet said, “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.”
These days have great excellence and superiority over all other days. These are the days right before Eid-ul-Adha, or the Hajj days, as we know them. One should maximize their good deeds in these days to benefit most from them.
I’ve written a detailed post on it once before, taken from Dr. Farhat Hashmi’s mind-blowing lecture on the subject. Do read! :)