Narrated `Abdullah bin Abu `Aufa:A man displayed some goods in the market and swore by Allah that he had been offered so much for that, that which was not offered, and he said so, so as to cheat a Muslim. On that occasion the following Verse was revealed: "Verily! Those who purchase a small gain at the cost of Allah's covenant and their oaths (They shall have no portion in the Hereafter ..etc.)' (3.77)
حَدَّثَنَا عَمْرُو بْنُ مُحَمَّدٍ، حَدَّثَنَا هُشَيْمٌ، أَخْبَرَنَا الْعَوَّامُ، عَنْ إِبْرَاهِيمَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي أَوْفَى ـ رضى الله عنه ـ أَنَّ رَجُلاً، أَقَامَ سِلْعَةً، وَهُوَ فِي السُّوقِ، فَحَلَفَ بِاللَّهِ لَقَدْ أَعْطَى بِهَا مَا لَمْ يُعْطَ، لِيُوقِعَ فِيهَا رَجُلاً مِنَ الْمُسْلِمِينَ، فَنَزَلَتْ {إِنَّ الَّذِينَ يَشْتَرُونَ بِعَهْدِ اللَّهِ وَأَيْمَانِهِمْ ثَمَنًا قَلِيلاً }
Bukhari
Sales and Trade • Hadith 41