Who has the most right to lower the deceased into their grave: the knowledgeable person or the guardian of the deceased? Does the ruling differ between a man and a woman? Is it a condition that the one who lowers a woman must be one of her unmarriageable kin (mahrams)?

The guardian of the deceased should be the one to lower the body into the grave. If there is no guardian, then the closest of his relatives should do so. A knowledgeable person is more entitled, but if there is none, then an unlearned person should seek guidance from a learned one. It is not a condition for the person lowering a woman into her grave to be her mahram (definition). The Prophet, peace and blessings be upon him, commanded Abu Talha to descend into his daughter's grave to bury her in the presence of himself and her husband.