When the Prophet ﷺ placed the dead in the grave, he said: In the name of Allah, and following the Sunnah of the Messenger of Allah ﷺ. This is Muslim's version. (Using translation from Abū Dāʾūd 3213)
أَنَّ النَّبِيَّ ﷺ كَانَ إِذَا وَضَعَ الْمَيِّتَ فِي قَبْرِهِ قَالَ بِسْمِ اللهِ وَعَلَى سُنَّةِ رَسُولِ اللهِ ﷺ وَهَذَا لَفْظُ مُسْلِمٍ