Kahmas b. al-Hasan said to me: “I committed a sin for which I have been crying in regret for forty years.” I asked: ‘What was it?’ He said: ‘A friend of mine visited me once so I bought for him a fish (to serve it to him). After he ate I stood up and took a piece of mud from the wall of my neighbor so he could use to wash his hand. This sin [taking the piece of mud without asking the permission of my neighbor] is what I have been crying about for forty years.”

Related by ‘Amaarah b. Zhaadhaan

Hilyah al-Awliya’ (6/211)

(Read on pg 47, Ibn al-Jawzi, Disturber of the Hearts. Dar As-Sunnah Publishers. Birmingham:2012.)