The Messenger of Allah ﷺ said, "None of you should sell over the sale of another, and do not intercept goods before they reach the markets."
حدثنا عبد الله بن مسلمة القعنبي عن مالك عن نافع
أن رسول الله ﷺ قال لا يبع بعضكم على بيع بعض ولا تلقوا السلع حتى يهبط بها الأسواق
Reported by Bukhari in the Book of Sales, chapter "A man should not sell over the sale of his brother," hadith no. 2165, and by Muslim in the Book of Sales, chapter on the prohibition of a man selling over another's sale, hadith no. 1514, from the hadith of Malik through this chain. It is also found in Muwatta (Yahya's recension), 2/683.