Riyad us Saliheen: Hadith 1374

Makhramah Al-'Abdi and I procured some drapery from Hajar and brought them to Makkah. The Prophet (ﷺ) came and bargained with us for some trousers and we sold them to him. We had a person who weighed the cloth in order to fix the price. The Prophet (ﷺ) said to him, "Weigh and add a little to it."

[Abu Dawud and At- Tirmidhi].