Abd al-Rahman bin Abi Nu'm narrates that Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) met Sayyiduna Ibn Abbas (may Allah be pleased with them both) and testified concerning the Messenger of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Gold for gold and silver for silver, like for like; whoever gives more has dealt in usury (riba)." Then Ibn Abbas (may Allah be pleased with them both) said: "I repent to Allah, the Mighty and Majestic, of the verdict I used to give." Then he retracted (his verdict).
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 451