Musannaf Ibn Abi Shayba 1:1304

Waki’ and Abu Mu’awiyah narrated to us, from al-A’mash, from Mujahid, from Tawus, from Ibn Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) passed by two graves and said: "Indeed, they are both being punished, and they are not being punished for something major." "As for one of them, he used to not cleanse himself from his urine. And as for the other, he used to walk about with slander."