Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him): "There is no fara' and no atirah." Fara' is a young animal which, after it was born, they used to slaughter in the name of idols, and atirah is an animal that was slaughtered in the month of Rajab.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19347