Sunan Abi Dawud
Hadith #4848
Amr b. al-Sharid quoted his father al-Sharid b. Suwaid as saying:The Messenger of Allah (ﷺ) came upon me when I was sitting thus: having my left hand behind my back and leaning on the fleshy part of it, and said: Are you sitting in the manner of those with whom Allah is angry?