From Sahih Muslim (Hadith 4068):
Abu Huraira (Allah be pleased with him) reported Allah's Mess-., nger (ﷺ) as saying:Gold is to be paid for by gold with equal weight, like for like, and silver is to be paid for by silver with equal weight, like for like. He who made an addition to it or demanded an addition dealt in usury
Reference: Muslim 4068