Narrated 'Amr bin al-'Aas (RA):

"Do not confuse us about our Prophet's Sunnah: The period that a slave-woman, whose master dies, and she has begotten a child from him must wait for, is four months and ten days." [Reported by Ahmad, Abu Dawud and Ibn Majah. al-Hakim graded it Sahih (authentic), but ad-Daraqutni considered it defective due to Inqita' (broken link)].

وَعَنْ عَمْرِو بْنِ الْعَاصِ قَالَ: { لَا تُلْبِسُوا عَلَيْنَا سُنَّةَ نَبِيِّنَا, عِدَّةُ أُمِّ اَلْوَلَدِ إِذَا تُوُفِّيَ عَنْهَا سَيِّدُهَا أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا } .‏ رَوَاهُ أَحْمَدُ, وَأَبُو دَاوُدَ, وَابْنُ مَاجَهْ, وَصَحَّحَهُ اَلْحَاكِمُ, وَأَعَلَّهُ اَلدَّارَقُطْنِيُّ بِالِانْقِطَاعِ [1]‏ .‏