The Angels Washed Adam
The Prophet (sal Allahu alaihi wa sallam) said: “When Adam died, the angels washed his body with water an odd number of times, then they buried him in a grave with a niche (Lahd), and said, ‘This is the way of the sons of Adam.’” [Mustadrak Al-Haakim]
The method of disposing off of the body of the deceased is one of the many things taught to humans by angels. When Adam (alaihis salam) died, his children did not know what they should do with his body, so the angels taught them.
This hadith informs us that it is recommended to wash the body of the deceased with water an odd number of times. It also tells us that it is preferable to bury the deceased in a grave that has a niche (Lahd) in the side of it, into which the body is placed. This way the earth doesn’t go directly on the body when the grave is closed.