Do not confuse us about his Sunnah. Ibn al-Muthanna said: The Sunnah of our Prophet ﷺ is that the waiting period of a slave-mother whose husband has died is four months and ten days.  

ابْنُ الْمُثَنَّى سُنَّةَ نَبِيِّنَا ﷺ عِدَّةُ الْمُتَوَفَّى عَنْهَا أَرْبَعَةُ أَشْهُرٍ وَعَشْرٌ يَعْنِي أُمَّ الْوَلَدِ  

[Machine] "Do not impose upon us the custom of our Prophet when his wife, the mother of his child, dies, for he mourned for her for four months and ten days."  

لَا تَلْبِسُوا عَلَيْنَا سُنَّةَ نَبِيِّنَا عِدَّةُ أُمِّ الْوَلَدِ إِذَا تُوُفِّيَ عَنْهَا سَيِّدُهَا أَرْبَعَةُ أَشْهُرٍ وَعَشْرٌ  

"Do not corrupt the Sunnah of our Prophet Muhammad ﷺ. The waiting period of an Umm Walad is four months and ten (days)." (Using translation from Ibn Mājah 2083)   

«لَا تُلَبِّسُوا عَلَيْنَا سُنَّةَ نَبِيِّنَا مُحَمَّدٍ ﷺ فِي أُمِّ الْوَلَدِ إِذَا تُوُفِّيَ عَنْهَا سَيِّدُهَا عِدَّتُهَا أَرْبَعَةُ أَشْهُرٍ وَعَشْرًا»