Sahih al-Bukhari, Book 34, Hadith 40 (In-Book) ⓘ
Narrated Abu Huraira: I heard Allah's Messenger saying, "The swearing (by the seller) may persuade the buyer to purchase the goods but that will be deprived of Allah's blessing."
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ يُونُسَ، عَنِ ابْنِ شِهَابٍ، قَالَ ابْنُ الْمُسَيَّبِ إِنَّ أَبَا هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " الْحَلِفُ مُنَفِّقَةٌ لِلسِّلْعَةِ مُمْحِقَةٌ لِلْبَرَكَةِ " .
also referenced under: Hadith 2087 (DarusSalam) & Volume 3, Book 34, Hadith 300 (USC-MSA)