Hadith: There are no days in which righteous deeds are more beloved to Allah than on these days," referring to the first ten days of Dhul-Hijjah

عن ابن عباس رضي الله عنهما قال: قال رسول الله صلى الله عليه وسلم:
«ما مِنْ أيَّامٍ العمَلُ الصَّالِحُ فيها أحبُّ إلى اللهِ مِن هذه الأيام» يعني أيامَ العشر، قالوا: يا رسُولَ الله، ولا الجهادُ في سبيلِ الله؟ قال: «ولا الجهادُ في سبيلِ الله، إلا رجلٌ خَرَجَ بنفسِه ومالِه فلم يَرْجِعْ من ذلك بشيءٍ».
[صحيح] - [رواه البخاري وأبو داود، واللفظ له] - [سنن أبي داود: 2438]

Ibn ‘Abbās (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) said:
"There are no days in which righteous deeds are more beloved to Allah than on these days," referring to the first ten days of Dhul-Hijjah. They said: "O Messenger of Allah, not even Jihad in the cause of Allah?" He said: "Not even Jihad in the cause of Allah, except that of a man who goes out (to Jihad) with his self and his property but returns with none of them."
[Authentic hadith] - [Narrated by Bukhari & Abu Daoud, the wording for the latter] - [Sunan Abu Daoud - 2438]

Explanation

The Prophet (may Allah's peace and blessings be upon him) points out that good deeds in the first ten days of the month of Dhul-Hijjah are better than those performed during the other days of the year.
The Companions (may Allah be pleased with them) asked the Prophet (may Allah's peace and blessings be upon him) about Jihad in the cause of Allah outside these ten days, as to whether it is better or the good deeds performed in these days. This is because it was well established among them that Jihad is one of the best deeds.
In response, the Prophet (may Allah's peace and blessings be upon him) said that good deeds on these days are better than Jihad performed on other days, with the exception of a man who goes out for Jihad and risks his life and property for the cause of Allah and he loses both his property and life. This is what is better than good deeds in these virtuous days.