Ibn 'Abbas (May Allah be pleased with them) said:
The Messenger of Allah (ﷺ) 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].
App reference: Book 18, Hadith 27
Arabic/English book reference: Book 18, Hadith 1537