- It is a Sunnah.
- It is the right of the deceased.
- A person attending the ṣalāh will receive reward equivalent to Mount Uḥud and the one who stays till the burial will receive reward equivalent to two Mount Uḥuds.
- It is a means of comfort for the family of the deceased.
- It causes us to remember our death.
Source: https://islambestreligion.wordpress.com/2011/07/22/what-are-the-five-benefits-of-attending-a-funeral-janazah/