I was with the Messenger of Allah ﷺ when deeds were mentioned, and he said, "There are no days in which righteous deeds are more beloved to Allah than these ten."The people asked, "Messenger of Allah, not even striving in the path of Allah?"He considered the question weighty, then replied, "Not even striving in the path of Allah, except for a man who goes out with himself and his wealth in the path of Allah, and the lifeblood of his soul is poured out in it."
كنت عند رسول الله ﷺ قال: فذكرت الأعمال، فقال: ما من أيام العمل فيهن أفضل من هذه العشر. قالوا: يا رسول الله، ولا الجهاد في سبيل الله؟ قال: فأكبره، فقال: ولا الجهاد إلا أن يخرج رجل بنفسه وماله في سبيل الله، ثم تكون مهجة نفسه فيه.
Ahmad (6559), Ibn Abu Asim in Jihad (157), and Tayalisi (2397) all narrated it from the hadith of Zuhayr bin Muawiya, who said, Ibrahim bin Muhajir told us, from Abdullah bin Babah, from Abdullah bin Amr, and he mentioned it. Its chain is hasan due to the disagreement about Ibrahim bin Muhajir, whom Abu Hatim graded daif while Ahmad, Abu Dawud, Ajli, Ibn Saad and others considered him acceptable, and he is hasan al-hadith.The word "mahjah," with a damma on the mim and a sakin on the ha, means blood, or the blood of the heart and the soul.Ibn Umar and Abu Hurairah used to go out to the marketplace during the first ten days, saying the takbir aloud, and the people would say the takbir along with them, and Muhammad bin Ali used to say the takbir after the additional prayer. Bukhari mentioned all of this in his Sahih, in the chapter on the merit of good deeds during the days of Tashriq, in the Book of the Two Eids.Ibn Hajar said, "What appears clear is that the reason for the special distinction of the first ten days of Dhul-Hijjah is that the principal acts of worship come together in it, namely prayer, fasting, charity, and Hajj, and this cannot be achieved in any other period." Fath al-Bari (2/460).Many scholars have recommended fasting during these excellent days, apart from the Day of Sacrifice. Nawawi, may Allah have mercy on him, said that it is strongly recommended.