I asked Al-Bara' bin ʿAzib and Zaid bin Arqam about money exchanges. Each of them said, "This is better than I," and both of them said, "Messenger of Allah ﷺ forbade the selling of silver for gold on credit. "  

عَنِ الصَّرْفِ فَكُلُّ وَاحِدٍ مِنْهُمَا يَقُولُ هَذَا خَيْرٌ مِنِّي فَكِلاَهُمَا يَقُولُ نَهَى رَسُولُ اللَّهِ ﷺ عَنْ بَيْعِ الذَّهَبِ بِالْوَرِقِ دَيْنًا