Ibn `Abbas (May Allah be pleased with them) said:
The Messenger of Allah (Sallallahu Alaihi Wasallam)
passed by two graves and said,
"Both of them (the persons in these graves) are being tortured,
and they are not being tortured for a cardinal sin.
But indeed they are great sins.
One of them used not to save himself from being soiled with his urine,
and the other one used to go about with calumnies
(among the people to rouse hostilities, e.g., one goes to a person
and tells him that so-and-so says about him such and such evil things).''
[Al-Bukhari and Muslim].

Commentary:
1. "La yastatiru min baulihi'' has another meaning, namely: "he does not pass
urine in privacy but does it shamelessly in the presence of other people.
'' Obviously shamelessness is also a sin. Talebearing, carelessness in saving
oneself from splash of urine drops, and lack of observance of privacy are sins
which are liable to punishment.

2. The Hadith also proves punishment in the grave