The Prophet (ﷺ) said, "Neither Fara' nor 'Atira) is permissible)." Al-Fara' was the first offspring (they got
of camels or sheep) which they (pagans) used to offer (as a sacrifice) to their idols. 'Atira was (a sheep
which used to be slaughtered) during the month of Rajab.
Sahih al-Bukhari Book 71, Hadith 9