"A man said: 'O Messenger of Allah, we used to sacrifice the 'Atirah during the Jahiliyyah in Rajab; what do you command us to do?' He said: 'Sacrifice to Allah, the Mighty and Sublime, whatever month it is, do good for the sake of Allah, the Mighty and Sublime, and feed (the poor)."'
Sunan an-Nasa'i Book 41, Hadith 11