Muwatta Imam Malik Book of Business Transactions, Hadith 32

Yahya related to me from Malik that he had heard from his grandfather, Malik ibn Abi Amir that Uthman ibn Affan said, "The Messenger of Allah ﷺ said to me, 'Do not sell a dinar for two dinars nor a dirham for two dirhams.' "

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ عَنْ جَدِّهِ، مَالِكِ بْنِ أَبِي عَامِرٍ أَنَّ عُثْمَانَ بْنَ عَفَّانَ، قَالَ قَالَ لِي رَسُولُ اللَّهِ ﷺ " لاَ تَبِيعُوا الدِّينَارَ بِالدِّينَارَيْنِ وَلاَ الدِّرْهَمَ بِالدِّرْهَمَيْنِ " .