Muwatta Malik 1253
موطأ مالك#1253SahihThese are the words of a Companion, not of the Prophet ﷺ. The chain is graded on its own terms.
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, "The idda of an umm walad when her master dies is one menstrual period
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Salim al-HilaliMauquf Sahih
In-book reference: 29:50