'Aishah (RAA) narrated, "Allah's Messenger (ﷺ) commanded them to slaughter two sheep equal (in age) for a boy and one for a girl at their birth.' Related by At-Tirmidhi and graded it as Sahih.

وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا; { أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-أَمْرَهُمْ; أَنْ يُعَقَّ عَنْ اَلْغُلَامِ شَاتَانِ مُكَافِئَتَانِ, وَعَنْ اَلْجَارِيَةِ شَاةٌ } رَوَاهُ اَلتِّرْمِذِيُّ وَصَحَّحَه ُ (1780)‏ .‏