Q) What is the ruling on sprinkling water on the grave after burying the dead, justifying this by saying that it makes the dust solid on the grave? Does it make it cool for the dead?
A) Praise be to Allaah.
There is nothing wrong with sprinkling water, because water holds the earth together so it will not be scattered right and left.
With regard to what the common folk believe, that sprinkling water cools down the deceased, there is no basis for this. End quote.
Majmoo’ Fataawa Ibn ‘Uthaymeen (17/194).