Musnad Ahmad Hadith 20731

It is narrated from Mukhnif bin Sulaym that we were present with the Prophet (peace be upon him) when he was standing in the plain of Arafat, and the Prophet (peace be upon him) was saying: O people, every year sacrifice (Qurbani) and 'Atirah are obligatory upon every household. The narrator asked: Do you know what is meant by 'Atirah? It is the same sacrifice which people also call Rahbiyah. Benefit: In the beginning, from the time of ignorance, the custom of sacrifice in the month of Rajab was prevalent; it was called 'Atirah and Rahbiyah. Later, it was prohibited, and only the sacrifice on the occasion of Eid al-Adha remained prescribed.