Musannaf Ibn Abi Shaybah 36986 — The words of Sulayman bin Dawud

Yahya bin Abi Kathir said: Sulayman bin Dawud (peace be upon them both) said to his son (advising him to take care in dealings): "O my dear son, just as a peg enters between two stones (in a barely noticeable way), so too sin enters between the buyer and the seller (in a barely noticeable way)."