I prayed over a dead person along with Ibn 'Abbas. He recited Surat al-Fatihah and he said: This is the Sunnah.
Sunan Abi Dawud Book 21, Hadith 110
← Previous Hadith Zaid b. Arqam used to utter four takbirs (Allah is Most Great) over our dead person (during prayer). He uttered five takbirs on a dead person. So I asked him. He replied: The Messenger of Allah (ﷺ) used to utter those.

Abu Dawud said: I remember the tradition of Ibn al-Muthanna in a more guarded way.

Sunan Abi Dawud Book 21, Hadith 109 Next Hadith → The Prophet (ﷺ) said: When you pray over the dead, make a sincere supplication for him.

Sunan Abi Dawud Book 21, Hadith 111