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.”
[Al- Bukhari].
The above is just a translation for the meaning in English, and here is the original speech of the Messenger of Allah (ﷺ) in Arabic:
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)).