(4) باب الْعَتِيرَةِ
Narrated Abu Huraira:
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.
Reference: Sahih al-Bukhari 5474
In-book reference: Book 71, Hadith 10
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 66, Hadith 383