It was narrated that Suwaid bin Qais said:
"Makhrafah Al' Abdi and I brought linens from Hajar[1] The Messenger of Allah (ﷺ) came to us to bargain with us with some trousers. There was someone with me who weighed (the goods) in exchange for a wage. So the Prophet (ﷺ) said to the one weighing: 'Weigh and add more.'" (TR)
English reference (TR): Vol. 3, Book 12, Hadith 2220 (TR)
Arabic reference (TR): Book 12, Hadith 2305 (TR)