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