He heard the Messenger of Allah ﷺ say, "Beware of swearing oaths frequently in business transactions, for it may help sell the goods, but it wipes out the blessing."
Azami 5681
Sahih
عن أبي قتادة الأنصاري
أنه سمع رسول الله ﷺ يقول: إياكم وكثرة الحلف في البيع؛ فإنه ينفق، ثم يمحق.
Muslim narrated it in the Book of Musaqah (1607) via Abu Usama (who is Hammad bin Usama), from Walid bin Kathir, from Mabad bin Kaab bin Malik, from Abu Qatada Ansari, who related it.