Question: How many people should go into the grave to lower the deceased? What is the masnoon doa to read when lowering the body?

Answer: It is not Sunnah to have an odd number of people to place the deceased into the grave. Four people lowered Rasoolullah Sallallahu alaihi wasallam into his grave.

It is Mustahabb to recite بسم الله وعلي ملة رسول الله (Bismillahi wa ala millati Rasoolillah) when lowering the deceased.