Qasim reports that I heard Abdullah ibn Abbas (may Allah be pleased with him) being asked by a man about a person who made a salam sale in garments and wanted to sell them before becoming their owner. Ibn Abbas (may Allah be pleased with him) said: "This is like selling silver for silver," and he disliked this sale. Imam Malik (may Allah have mercy on him) said: "In our opinion, since he wanted to sell it at a higher price to the same person with whom he made the sale, (that is why it was disliked), and if he sells it to someone other than the one from whom he bought the goods, then there is no harm in this sale."
Hadith Referenceمسند الإمام الشافعي / كتاب البيوع / 1444
Hadith Takhrijاسناده صحیح اخرجه مالك فى الموطا، البيوع، باب السلف في العروض۔