بُلُوغُ الْمَرَامِ
Bulugh al-Maram 834
Business Transactions
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ اَلذَّهَبُ بِالذَّهَبِ وَزْناً بِوَزْنٍ مِثْلًا بِمِثْلٍ، وَالْفِضَّةُ بِالْفِضَّةِ وَزْناً بِوَزْنٍ مِثْلًا بِمِثْلٍ, فَمَنْ زَادَ أَوْ اِسْتَزَادَ فَهُوَ رِبًا } رَوَاهُ مُسْلِمٌ [1] .
Narrated Abu Hurairah (RA): Allah's Messenger (ﷺ) said: "Gold is to be paid for with gold, both being of equal weight and of same quantities; silver is to be paid for with silver, both being of equal weight and of same quantities. If anyone gives more or asks for more of it, it is then usury." [Reported by Muslim].
Sunnah.com reference: Book 7, Hadith 67