Mahkrafah al-Abdi and I brought some cloth from Hajar and carried it to Mecca. The Messenger of Allah ﷺ came to us walking and bargained with us for a pair of trousers, which we sold to him. There was a man there who weighed goods for a fee, and the Messenger of Allah ﷺ said to him, "Weigh it out, and tip the scale in his favor."
حدثنا عبيد الله بن معاذ حدثنا أبي حدثنا سفيان عن سماك بن حرب
جلبت أنا ومخرفة العبدي بزا من هجر فأتينا به مكة فجاءنا رسول الله ﷺ يمشي فساومنا بسراويل فبعناه وثم رجل يزن بالأجر فقال له رسول الله ﷺ زن وأرجح
Sourcing, sahih. Tirmidhi narrated it in the Book of Business Transactions, Chapter on What Has Been Said Regarding Adding Extra Weight, hadith 1305, from the hadith of Sufyan Thawri, and said, hasan sahih. Nasai also narrated it, hadith 4596, as did Ibn Majah, hadith 2220, 2222, 3579. Ibn Hibban graded it sahih, hadith 1444, as did Ibn Jarud, hadith 559. The hadith has other transmission routes.