Sahih al-Bukhari
Sahih al-Bukhari 2180, 2181
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي حَبِيبُ بْنُ أَبِي ثَابِتٍ، قَالَ سَمِعْتُ أَبَا الْمِنْهَالِ، قَالَ سَأَلْتُ الْبَرَاءَ بْنَ عَازِبٍ وَزَيْدَ بْنَ أَرْقَمَ ـ رضى الله عنهم ـ عَنِ الصَّرْفِ،، فَكُلُّ وَاحِدٍ مِنْهُمَا يَقُولُ هَذَا خَيْرٌ مِنِّي. فَكِلاَهُمَا يَقُولُ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم عَنْ بَيْعِ الذَّهَبِ بِالْوَرِقِ دَيْنًا.
Hafs ibn Umar narrated to us: Shuba narrated to us; he said: Habib ibn Abi Thabit informed me; he said: I heard Abu al-Minhal say: I asked al-Bara ibn Azib and Zayd ibn Arqam, may Allah be pleased with them, about currency exchange. Each of them said, “He is more knowledgeable than I am.” Both of them said: The Messenger of Allah forbade selling gold for silver on credit.
Translation notes
Both Companions defer to the other as more knowledgeable, then agree on the prohibition they heard. The Arabic refers to gold exchanged for silver on credit.