Muawiyah sold a cup of gold or silver for more than its weight. Abu Ad-Darda' said: "I heard the Messenger of Allah forbid such transactions unless it was like for like." (Using translation from Nasāʾī 4572)
أَنَّ مُعَاوِيَةَ بَاعَ سِقَايَةً مِنْ ذَهَبٍ أَوْ وَرِقٍ بِأَكْثَرَ مِنْ وَزْنِهَا فَقَالَ أَبُو الدَّرْدَاءِ سَمِعْتُ رَسُولَ اللهِ ﷺ يَنْهَى عَنْ مِثْلِ هَذَا إِلَّا مِثْلًا بِمِثْلٍ