Who is the one who should lower the deceased into the grave?
Question

                Who is the most entitled of people to lower the deceased into the grave, the one who has knowledge or the next of kin of the deceased? Is there a difference between men and women? Is it essential that the one who lowers a woman into her grave be one of her mahrams?.
Praise be to Allah.Shaykh Muhammad ibn ‘Uthaymeen (may Allaah 
    have mercy on him) said: 
The one who is more entitled to do that is 
    the one whom the deceased wanted to do that for him, if he expressed a preference. If he did not express a preference, then it should be the next 
    of kin. If there is one who is knowledgeable then he is more entitled, and if there is no one who is knowledgeable, then he may learn from one who 
    is knowledgeable, and the one who is knowledgeable may direct the one who has no knowledge to carry out this task. 
It is not essential for the one who lowers 
    the deceased into the grave to be a mahram of the woman. The Prophet  (peace and blessings of Allaah be upon him) commanded Abu Talhah (may Allaah be pleased with him) to go down into the grave of his (the Prophet’s) daughter and bury her in his presence and in the presence of her husband ‘Uthmaan ibn ‘Affaan (may Allaah be pleased with him). (The hadeeth was narrated by al-Bukhaari, 1342).