Imam Al-Nawawi's Riyad-us-Saliheen
Chapter 226
The Excellence of As-Saum (The Fast) during the first ten Days of Dhul-Hijjah

1249. Ibn `Abbas (May Allah be pleased with them) reported: The Messenger of Allah (sallallaahu ’alayhi wa sallam) said, "There are no days during which the righteous action is so pleasing to Allah than these days (i.e., the first ten days of Dhul-Hijjah).'' He was asked: "O Messenger of Allah, not even Jihad in the Cause of Allah?'' He (sallallaahu ’alayhi wa sallam) replied, "Not even Jihad in the Cause of Allah, except in case one goes forth with his life and his property and does not return with either of it.''
[Al-Bukhari].

Commentary:  This Hadith brings out the following two points:

1. Righteous deeds during the first ten days of the month of Dhul-Hijjah are far better and more rewarding than righteous deeds done on other days of the year, because they are Hajj days in the sacred season of pilgrimage. Because of their excellence and importance, Allah (SWT) swore by them, thus: "By the Dawn; by the ten Nights...'' (89:1,2)

2. Jihad has great eminence in Islam.