Narrated Al-Shabi: The Messenger of Allah ﷺ passed a grave dug freshly. They arranged a row and uttered four takbirs over it. I asked al-Shabi: Who told you ? He replied: A reliable person whom Abdullah bin Abbas attended.
Hadith Referenceسنن ابي داود / كتاب الجنائز / 3196
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح بخاري (1247) صحيح مسلم (954)
Narrated Ibn Abi Laila: Zaid bin 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.
Hadith Referenceسنن ابي داود / كتاب الجنائز / 3197
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم (957)