Sayyiduna Qays bin Abi Gharazah (may Allah be pleased with him) said: We used to buy and sell in Madinah and we used to call ourselves 'samasirah'. Then the Messenger of Allah (peace and blessings be upon him) came to us and gave us a better name than the one we had given ourselves, and said: "O traders, idle talk and oaths get mixed into this buying and selling, so mix it with some charity."
Hadith Referenceالمعجم الكبير للطبراني / باب القاف / 15999