It was narrated from Anas that the Prophet (ﷺ) offered the funeral prayer at a grave after the burial.
Sunan Ibn Majah Book 6, Hadith 99
← Previous Hadith “A man died whom the Messenger of Allah (ﷺ) used to visit, and they buried him at night. When morning came, they told him. He said: ‘What kept you from telling me?’ They said: ‘It was night and it was dark, and we did not like to cause you any inconvenience.’ Then he went to the grave and offered the funeral prayer for him.”

Sunan Ibn Majah Book 6, Hadith 98 Next Hadith → 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.

Sunan Ibn Majah Book 6, Hadith 100