مسند أحمد

Sa`eed bin al-Musayyab said. I heard ‘Uthman (رضي الله عنه) delivering a khutbah from the minbar. He said: I used to buy dates from one of the Jewish clans who were called Banu Qainuqa`, and sell them at a profit. News of that reached the Messenger of Allah (ﷺ) who said: `O `Uthman, when you buy, take your dues with nothing extra, and when you sell, give (the other party`s) dues with nothing less.`

Moosa bin Wardan narrated from Sa`eed bin al-Musayyab from ‘Uthman bin `Affan (رضي الله عنه)... and he mentioned a similar report.