Full Sharh — Riyad as-Salihin 570
وعن ابن عباس رضي الله عنهما قال: قال رسول الله صلى الله عليه وسلم: " ما من أيام العمل الصالح فيها أحب إلى الله من هذه الأيام" يعني أيام العشر، قالوا: يا رسول الله ولا الجهاد في سبيل الله؟ قال: "ولا الجهاد في سبيل الله، إلا رجل خرج بنفسه، وماله فلم يرجع من ذلك بشيء" ((رواه البخاري)).
English Translation
Ibn 'Abbas (May Allah be pleased with them) reported:: The Messenger of Allah (ﷺ) 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 (ﷺ) 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.".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Virtues
Hadith Number
570