The first ten days of Dhul-Hijjah are widely considered the most virtuous days of the year for righteous deeds. Many scholars rank them spiritually equal to or even surpassing the last ten nights of Ramadan, on the principle that the days of Ramadan are best for night worship while the first ten days of Dhul-Hijjah are best for daytime worship.

The Qur’an swears by these days at the opening of Surah al-Fajr: “By the dawn. And [by] ten nights.” (Surah al-Fajr 89:1-2). The majority of classical commentators, including Ibn Kathir and at-Tabari, identify these “ten nights” as the first ten of Dhul-Hijjah. The Qur’an also refers to “appointed days” on which Allah’s name is to be remembered (Surah al-Hajj 22:28).

The Prophet (peace be upon him) said: “No good deeds done on other days are superior to those done on these (first ten days of Dhul Hijja).” Then some companions of the Prophet (ﷺ) said, “Not even Jihad?” He replied, “Not even Jihad, except that of a man who does it by putting himself and his property in danger (for Allah’s sake) and does not return with any of those things.”“ (Sahih al-Bukhari 943).

Recommended worship in these ten days includes fasting on as many of the first nine days as possible (especially the Day of Arafah on the 9th), increased recitation of the Qur’an, charity, the takbir (Allahu akbar), tahlil (la ilaha illa Allah), and tahmid (al-hamdu lillah). The Prophet (peace be upon him) said: “There are no days greater in the sight of Allah, nor any in which good deeds are more beloved to Him, than these ten days. So during them say a great deal of tahlil, takbir, and tahmid.” (Musnad Ahmad 5446).

The tenth day of Dhul-Hijjah is Eid al-Adha, on which fasting becomes prohibited. So while fasting is recommended for the first nine days, the ten days as a unit conclude with the festival of sacrifice. This is also the period in which Muslims around the world stand with the pilgrims in spirit, even if they are not performing Hajj themselves.