Ibn Abu Mulaika narrates: Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) came to Sayyiduna Abdullah bin Umar (may Allah be pleased with them both). He greeted him with salam and asked: Do you accuse Sayyiduna Usama (may Allah be pleased with him)? The narrator states, so Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) replied: No, I do not. He informed: He has narrated this hadith to me: "Riba (usury) occurs only in credit transactions."
(Imam Ibn Hibban, may Allah have mercy on him, says:) The meaning of this narration is that when the six items mentioned in the hadith are sold for the same kind and there is an extra payment between them, then this is riba. But when they are sold for something other than their kind, and then whatever is extra is permissible as long as the transaction is hand to hand. But if it is a credit transaction, then it will be riba.