"Umar said: Dinar for Dinar, Dirham for Dirham, no difference between them, this is the obligation that our Prophet enjoined upon us."  

ابْنُ عُمَرَ الدِّينَارُ بِالدِّينَارِ وَالدِّرْهَمُ بِالدِّرْهَمِ لاَ فَضْلَ بَيْنَهُمَا هَذَا عَهْدُ نَبِيِّنَا ﷺ إِلَيْنَا  

"The Messenger of Allah said: 'Gold for gold, weight for weight, like for like; and silver for silver, weight for weight, like for like. Whoever gives more or takes more has engaged in Riba."'  

قَالَ رَسُولُ اللَّهِ ﷺ الذَّهَبُ بِالذَّهَبِ وَزْنًا بِوَزْنٍ مِثْلاً بِمِثْلٍ وَالْفِضَّةُ بِالْفِضَّةِ وَزْنًا بِوَزْنٍ مِثْلاً بِمِثْلٍ فَمَنْ زَادَ أَوِ ازْدَادَ فَقَدْ أَرْبَى