It was narrated from Ibn Buraidah from his father that the Prophet ﷺ offered the funeral prayer for a deceased person after he had been buried. (Using translation from Ibn Mājah 1532)

أَنَّ النَّبِيَّ ﷺ «صَلَّى عَلَى مَيِّتٍ بَعْدَ مَا دُفِنَ»