If you are not doing hajj, then fast for the 10 days and increase in ibadaah, as Allah swt takes an OATH on these 10 days. Marka there is nothing simply more important than them for the Muslims.
Allah says in the Qur'an:
"By the dawn and by the ten nights … " [Al-Qur'an 89:1-2]
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.
These ten days are better than all the other days of the year, with no exceptions, not even the last ten days of Ramadaan. But the last ten nights of Ramadaan are better, because they include Laylat al-Qadr.




