Language:
كتاب البيوع
34  
Sales and Trade
(27)
Chapter: Giving oaths (swearing) while selling
(27)
باب مَا يُكْرَهُ مِنَ الْحَلِفِ فِي الْبَيْعِ
Sahih al-Bukhari 2088

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 ‏}
Reference : Sahih al-Bukhari 2088
In-book reference : Book 34, Hadith 41
USC-MSA web (English) reference : Vol. 3, Book 34, Hadith 301
  (deprecated numbering scheme)