Full Sharh — Musnad Ahmad 527
حَدَّثَنَا أَبُو سَعِيدٍ، حَدَّثَنَا ابْنُ لَهِيعَةَ، أَخْبَرَنَا مُوسَى بْنُ وَرْدَانَ، قَالَ سَمِعْتُ سَعِيدَ بْنَ الْمُسَيَّبِ، يَقُولُ سَمِعْتُ عُثْمَانَ، يَخْطُبُ عَلَى الْمِنْبَرِ وَهُوَ يَقُولُ كُنْتُ أَبْتَاعُ التَّمْرَ مِنْ بَطْنٍ مِنْ الْيَهُودِ يُقَالُ لَهُمْ بَنُو قَيْنُقَاعٍ فَأَبِيعُهُ بِرِبْحِ الْآصُعِ فَبَلَغَ ذَلِكَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ يَا عُثْمَانُ إِذَا اشْتَرَيْتَ فَاكْتَلْ وَإِذَا بِعْتَ فَكِلْ.
English Translation
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.`
Source
Musnad Ahmad(مسند أحمد)
Musnad Uthman ibn Affan
Hadith Number
527