Mukhtasar Bukhari (Abridged) 930 — Both Eid months are never deficient

Narrated by Sayyiduna Abu Bakr (may Allah be pleased with him) from the Noble Prophet (peace and blessings of Allah be upon him) that he (peace be upon him) said: "There are two months that are not reduced; both months are of Eid: (1) Ramadan (2) Dhul-Hijjah."