Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated: I heard the Messenger of Allah (peace and blessings be upon him) say: "There is no deed more beloved to Allah than a deed done in these ten days (the first ten days of Dhu al-Hijjah), except for a man who went out to strive in jihad with his life and his wealth and then did not return."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12226