It was narrated from Abu Qatadah that the Messenger of Allah (ﷺ), said:
"Beware of swearing oaths when selling, for it may help you to make a sale but it destroys the blessing."' (AR)
English reference (AR): Vol. 3, Book 12, Hadith 2209 (AR)
Arabic reference (AR): Book 12, Hadith 2293 (AR)