حَدَّثَنَا عَبْدَانُ، حَدَّثَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا مَعْمَرٌ، أَخْبَرَنَا الزُّهْرِيُّ، عَنِ ابْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ لاَ فَرَعَ وَلاَ عَتِيرَةَ " وَالْفَرَعُ أَوَّلُ النِّتَاجِ، كَانُوا يَذْبَحُونَهُ لَطِوَاغِيتِهِمْ، وَالْعَتِيرَةُ فِي رَجَبٍ
Narrated Abu Huraira:
The Prophet (ﷺ) said, "Neither Fara' nor 'Atira (is permissible):" Al-Fara' nor 'Atira (is permissible):" Al- Fara' was the first offspring (of camels or sheep) which the pagans used to offer (as a sacrifice) to their idols. And Al-`Atira was (a sheep which was to be slaughtered) during the month of Rajab.
Reference: Sahih al-Bukhari 5473
In-book : Book 71, Hadith 9
USC-MSA web (English) : Vol. 7, Book 66, Hadith 382 (deprecated)