1. Allah honoured these days by taking an oath by them.
Allah (subḥānahū wa ta‘ālā) says: “By the Daybreak, and by 10 Nights.” (89:1-2)
According to the majority of the scholars, these 10 nights refer to the 10 days of Dhul Ḥijjah. When Allah swears an oath by something, it is an indication of its importance and benefit.
2. These are the best days of the year.
The Messenger of Allah ﷺ said: “There are no days on which righteous deeds are more beloved to Allah than these 10 days (the first 10 of Dhul Ḥijjah).” The (Ṣaḥābah) asked: “Not even jihād in the path of Allah?” The Messenger of Allah ﷺ replied: “Not even jihād in the path of Allah, unless a man goes out himself for jihād taking his wealth with him and does not return with anything from it.” (Tirmidhī)
The Messenger of Allah ﷺ also said: “There are no better days in the sight of Allah than the 10 days of Dhul Ḥijjah.” (Ibn Ḥibbān)
Scholars opine that the days of the first 10 days of Dhul Ḥijjah are superior to the last 10 days of Ramaḍān. However, there is a night in Ramaḍān which is superior to all other nights (i.e. Laylat al-Qadr).
Ibn Ḥajar (raḥimahullāh) said the reason that these 10 days are so special is because all of the major acts of worship occur in them, which doesn’t happen in other days: ṣalāh, fasting, charity and ḥajj. Although it is possible to combine the first three deeds on an ordinary day, the great worship of ḥajj is restricted to these blessed days.
3. They comprise of the Day of Arafah.
One of the main reasons for these days being extremely special is that they comprise of the Day of ʿArafah.
4. They comprise of the day of Nahr (sacrifice).
The Messenger of Allah ﷺ said: “The greatest day in the sight of Allah is the day of Naḥr (10th of Dhul Ḥijjah) and then the day of Qarr (11th of Dhul Ḥijjah).” (Abū Dāwūd)
The Day of Naḥr is the best day due to the various rites of ḥajj simultaneously occurring in it, such as the pelting of the jamārāt, shaving the head, sacrificing the animal, ṭawāf, and saʿy. Similarly, non-pilgrims gather for the ṣalāh of ʿEīd, congratulate one another and perform qurbānī.
‘Whoever missed out on standing in ʿArafah, then let him stand for Allah and fulfil His rights which he is aware of.
Whoever is unable to spend the night in Muzdalifah, then let him be strongly determined to obey Allah, as Allah has drawn him near.
Whoever could not stay in the vicinity of Masjid al-Khayf (in Mina), then let him stand for Allah with hope and fear.
Whoever is unable to slaughter his sacrificial offering in Mina, then let him slaughter his desires and reach his objective.
And whoever was unable to reach the House (Kaʿbah) due to its distance, then let him advance towards the Lord of the House – for He is closer to the one who supplicates to Him and has hope in Him than his jugular vein.’ -Ibn Rajab (raḥimahullāh)