It was narrated that Qais bin Abi Gharazah said:"In Al-Madinah we used to buy and sell Wasqs (of goods), and we used to call ourselves Samasir (brokers), and the people used to call us like that. The Messenger of Allah came out to us one day, and called us by a name that was better than that which we called ourselves and which the people called us. He said: 'O Tujjar (traders), your selling involves (false) oaths and lies, so mix some charity with it.'"
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، وَمُحَمَّدُ بْنُ قُدَامَةَ، قَالاَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ أَبِي وَائِلٍ، عَنْ قَيْسِ بْنِ أَبِي غَرَزَةَ، قَالَ كُنَّا بِالْمَدِينَةِ نَبِيعُ الأَوْسَاقَ وَنَبْتَاعُهَا وَكُنَّا نُسَمِّي أَنْفُسَنَا السَّمَاسِرَةَ وَيُسَمِّينَا النَّاسُ فَخَرَجَ إِلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم ذَاتَ يَوْمٍ فَسَمَّانَا بِاسْمٍ هُوَ خَيْرٌ مِنَ الَّذِي سَمَّيْنَا أَنْفُسَنَا وَسَمَّانَا النَّاسُ فَقَالَ " يَا مَعْشَرَ التُّجَّارِ إِنَّهُ يَشْهَدُ بَيْعَكُمُ الْحَلِفُ وَالْكَذِبُ فَشُوبُوهُ بِالصَّدَقَةِ " .
Nesai
The Book of Oaths and Vows • Hadith 3800