وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ قَالَ عِدَّةُ أُمِّ الْوَلَدِ إِذَا تُوُفِّيَ عَنْهَا سَيِّدُهَا حَيْضَةٌ ‏.‏

Malik related to me from Nafi that Abdullah ibn Umar said, "Theidda of an umm walad when her master dies is one menstrual period." Translation Not Available

Book Ref: Muwatta Imam Malik Book 29 Hadith 1256
Web Ref:  Muwatta Imam Malik Book 29 Hadith 92