The Messenger of Allah ﷺ passed a grave dug freshly. They arranged a row and uttered four takbirs over it. I asked al-Sha'bi: Who told you ? He replied: A reliable person whom 'Abd Allah b. 'Abbas attended.  

أَنَّ رَسُولَ اللَّهِ ﷺ مَرَّ بِقَبْرٍ رَطْبٍ فَصَفُّوا عَلَيْهِ وَكَبَّرَ عَلَيْهِ أَرْبَعًا فَقُلْتُ لِلشَّعْبِيِّ مَنْ حَدَّثَكَ قَالَ الثِّقَةُ مَنْ شَهِدَهُ عَبْدُ اللَّهِ بْنُ عَبَّاسٍ  

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.  

كَانَ رَسُولُ اللَّهِ ﷺ يُكَبِّرُهَا