Is Udhiyah obligatory or Sunnah?

Scholars differed as to whether it is Sunnah mu’akkadah (a confirmed Sunnah) or it is obligatory and it is not permissible to omit it.

The majority of scholars are of the view that it udhiyah is Sunnah mu’akkadah. This is the view of al-Shaafa’i, Maalik and Ahmad according to his most well-known view.

Others were of the view that it is obligatory. This is the view of Abu Haneefah and one of the views narrated from Ahmad. This was also the view favoured by Ibn Taymiyah who said:

“This is one of the views narrated in the madhhab of Maalik, or it appears to be the view of Maalik.”

(From Risaalat Ahkaam al-Udhiyah wa’l-Dhakaah by 
Ibn ‘Uthaymeen (may Allaah have mercy on him).

Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said:

“Udhiyah is Sunnah mu’akkadah for the one who is able to do it, so a person should offer the sacrifice on behalf of himself and the members of his household.”

 (Fataawa Ibn ‘Uthaymeen, 2/661)

Almighty Allah knows best.