Shaikh Abdul-Azeez Bin Baaz (rahimahullaah) was asked: ”What is your view on the view of the one who says that fasting during the first ten days of Dhul Hijja is an innovation?
This one is an ignoramus…
[Source: Majmoo Fataawaa 15/418]
Shaikh Muhammad Bin Saaleh Al-Uthaymeen (rahimahullaah) said:
We feel sorry for some of the people who bring doubt to the Muslims in this affair, saying that fasting it (i.e. the first ten days of Dhul-Hijja) is not a Sunnah. Glorified be Allaah! I fear that Allaah will punish them on the day of judgement (i.e. for uttering this statement). How can the Messenger (sallal-laahu-alayhi-wasallam) say that ‘’there are not any days in which righteous actions are done that are more beloved to Allaah than these ten days’’ and then we leave out the righteous deed about which Allaah has stated: ‘’Indeed it (i.e. fasting) is for Me and I will reward it’’…..
[Source: [Liqaa Ash-Shah’ree: Number: 199]