Musannaf Ibn Abi Shaybah

Hazrat Abdullah bin Abi Bakr narrates that when the deceased would be covered with soil and the grave leveled, Hazrat Anas would stand by the grave and supplicate as follows: O Allah! Your servant has been returned to You, so show kindness to him and have mercy on him. O Allah! Widen the grave for him from its side. And open the doors of the heavens for his soul. And accept his deeds in a good manner. O Allah! If he was righteous, then increase his good deeds twofold, and if he was a sinner, then forgive his sins.