Sunan an-Nasa'i, Hadith 4460 ⓘ
It was narrated from Abu Qatadah Al-Ansari that he heard the Messenger of Allah say: "Beware of taking oaths a great deal when selling, for it may help you to make a sale but it destroys the blessing."
أَخْبَرَنِي هَارُونُ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا أَبُو أُسَامَةَ، قَالَ أَخْبَرَنِي الْوَلِيدُ، - يَعْنِي ابْنَ كَثِيرٍ - عَنْ مَعْبَدِ بْنِ كَعْبِ بْنِ مَالِكٍ، عَنْ أَبِي قَتَادَةَ الأَنْصَارِيِّ، أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " إِيَّاكُمْ وَكَثْرَةَ الْحَلِفِ فِي الْبَيْعِ فَإِنَّهُ يُنَفِّقُ ثُمَّ يَمْحَقُ " .
also referenced under: Book 44, Hadith 12 (In-Book) & Volume 5, Book 44, Hadith 4465 (DarusSalam)