Sunan an-Nasa'i, Volume 5, Book 44, Hadith 4573 (DarusSalam) ⓘ
It was narrated that Abu Hurairah said: "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."'
أَخْبَرَنَا وَاصِلُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ فُضَيْلٍ، عَنْ أَبِيهِ، عَنِ ابْنِ أَبِي نُعْمٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الذَّهَبُ بِالذَّهَبِ وَزْنًا بِوَزْنٍ مِثْلاً بِمِثْلٍ وَالْفِضَّةُ بِالْفِضَّةِ وَزْنًا بِوَزْنٍ مِثْلاً بِمِثْلٍ فَمَنْ زَادَ أَوِ ازْدَادَ فَقَدْ أَرْبَى " .
also referenced under: Hadith 4569 (Reference) & Book 44, Hadith 121 (In-Book)