Imam Malik's Muwatta, Chapter: Business Transactions

Yahya related to me from Malik from Zayd ibn Aslam from Ata ibn Yasar that Muawiya ibn Abi Sufyan sold a gold or silver drinking-vessel for more than its weight. Abud Darda said, "I heard the Messenger of Allah, may Allah bless him and grant him peace, forbidding such sales except like for like." Muawiya said to him, "I don't see any harm in it." Abud Darda said to him, "Who will excuse me from Muawiya? I tell him something from the Messenger of Allah, may Allah bless him and grant him peace, and he gives me his own opinion! I will not live in the same land as you!" Then Abud Darda went to Umar ibn al-Khattab and mentioned that to him. Umar ibn al-Khattab therefore wrote to Muawiya, "Do not sell it except like for like, weight for weight."