Abu `Amr (also called Abu `Abdullah and also Abu Laila) from `Uthman bin `Affan (May Allah be pleased with him) reported:
After the burial of a dead man, the Prophet (ﷺ) would stand by the grave and say, "Ask Allah to forgive your brother and supplicate for him for steadfastness because he is being questioned (about his deeds) now."[Abu Dawud]. (FR)
App reference (FR): Book 7, Hadith 52 (FR)
Arabic/English book reference (FR): Book 7, Hadith 946 (FR)