The excellence of these ten days have been mentioned in the Qur’an and the Sunnah.
1. Allah says in the Qur’an:
“By the dawn and by the ten nights … ”
Ibn Kathir said that “the ten nights” referred to here are the ten days of Dhul-Hijjah, and this opinion was also held by Ibn Abbas, Ibn Az-Zubair, Mujahid and others.
2. The Messenger of Allah, SallAllahu Alaihi Wa Sallam, said:
“There are no deeds as excellent as those done in these ten days.”
They (the companions listening) said, “Not even Jihad?”
He, SallAllahu Alaihi Wa Sallam, said,
“No, not even Jihad except a man who goes forth endangering his life and wealth and does not return with anything.”
—Recorded by Imam Al-Bukhari
3. Allah says:
” … and remember the name of Allah in the appointed days.”
Ibn Abbas and Ibn Kathir said this means in the ten days of Dhul-Hijjah.
4. The Messenger of Allah, SallAllahu Alaihi Wa Sallam, said:
“There are no other days that are as great as these in the sight of Allah, the Most Sublime. Nor are there any deeds more beloved to Allah then those that are done in these ten days. So increase in tahlil (to say la illaha illallah), takbir (to say allahu akbar) and tahmid (to say alhumdulillah).”
—Reported by At-Tabarani in Al-Mu’jum al-Kabir
5. With regards to the noble companion Sa’id bin Jubayr, when the days of Dhu’l-Hijjah began he would strive to increase in good actions with great intensity until he was unable to increase anymore. [Reported by Ad-Darimi]
6. Ibn Hajar says in Fath al-Bari:
“The most apparent reason for the ten days of Dhu’l-Hijjah being distinguished in excellence is due to the assembly of the greatest acts of worship in this period, i.e. salawat (prayers), siyam (fasting), sadaqah (charity) and the Hajj (pilgrimage). In no other periods do these great deeds combine.”