Abu Al-Minhāl says that I asked Hazrat Bara’ (may Allah be pleased with him) and Zaid (may Allah be pleased with him) about the exchange of currency. Both of them said that during the blessed era of the Prophet Muhammad (peace and blessings be upon him), we used to trade. Once, we also asked him this same question, and he said: If the transaction is in cash, then there is no harm, but if it is on credit, then it is not correct.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19330
Hadith Gradingحکم دارالسلام:حديث صحيح، خ: 2180، م: 1589، وهذا إسناد ضعيف الانقطاعه، حسن بن مسلم لم يسمعه من أبى المنهال