Sahih al-Bukhari Book 34, Hadith 41
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)
I heard Allah's Messenger (ﷺ) saying, "The swearing (by the seller) may persuade the buyer to purchase the goods but that will be deprived of Allah's blessing."
I got an old she-camel as my share from the booty, and the Prophet (ﷺ) had given me another from Al- Khumus. And when I intended to marry Fatima (daughter of the Prophet), I arranged that a goldsmith from the tribe of Bani Qainuqa' would accompany me in order to bring Idhkhir and then sell it to the goldsmiths and use its price for my marriage banquet.