Riyad as-Salihin (The Meadows of the Righteous)
by Imam Nawawi
161. Chapter: On supplication for the deceased after his burial and staying at the grave for a time for supplication, asking forgiveness and recitation
946. Abu 'Amr, and it is said Abu 'Abdullah or Abu Layla, 'Uthman ibn 'Affan said, "When the Prophet, may Allah bless him and grant him peace, finished burying a dead person, he used to stand over him and say, 'Ask forgiveness for your brother and ask for steadfastness for him. Now he is being questioned.'" [Abu Dawud]
947. Abu 'Amr ibn al-'As said, "When you bury me, then stand around my grave for as long as it takes to slaughter a camel and divide its meat so that I can be comforted by you and see what answer I should make to the messengers of my Lord." [Muslim]
Ash-Shafi'i, may Allah have mercy on him, said, "It is recommended to recite some of the Qur'an in his presence. It is good if the entire Qur'an is recited in his presence."