عن أبي هريرة رضي الله عنه قال: قال رسول الله صلى الله عليه وسلم: أكثر عذاب القبر من البول (المستدرك للحاكم الرقم: 653)

Hazrat Abu Hurairah (radhiyallahu ‘anhu) reports that Hazrat Rasulullah (sallallahu ‘alaihi wasallam) said, “Most of the punishment (meted out to most people) in the grave will be on account of urine (i.e. being unmindful regarding urine splashes and impurities. Therefore, their wudhu, salaah and other ibaadaat will not gain acceptance due to them remaining impure).”