Whenever the Prophet ﷺ became free from burying the dead, he used to stay at him (i.e. his grave) and say: Seek forgiveness for your brother, and beg steadfastness for him, for he will be questioned now. Abu Dawud said: The full name of the narrator Buhair is Buhair b. Raisan.  

كَانَ النَّبِيُّ ﷺ إِذَا فَرَغَ مِنْ دَفْنِ الْمَيِّتِ وَقَفَ عَلَيْهِ فَقَالَ اسْتَغْفِرُوا لأَخِيكُمْ وَسَلُوا لَهُ التَّثْبِيتَ فَإِنَّهُ الآنَ يُسْأَلُ