Muwatta Imam Malik Book of Slaughtering Animals, Hadith 9

Yahya related to me from Malik from Yazid ibn Abdullah ibn Qusayt al-Laythi that Said ibn al- Musayyab said, "The slaughter of what is in the womb is included in the slaughter of the mother if it is perfectly formed and its hair has begun to grow."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَزِيدَ بْنِ عَبْدِ اللَّهِ بْنِ قُسَيْطٍ اللَّيْثِيِّ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّهُ كَانَ يَقُولُ ذَكَاةُ مَا فِي بَطْنِ الذَّبِيحَةِ فِي ذَكَاةِ أُمِّهِ إِذَا كَانَ قَدْ تَمَّ خَلْقُهُ وَنَبَتَ شَعَرُهُ .