"I used to sell gold for silver, or silver for gold. I came to the Messenger of Allah and told him about that, and he said: 'If you make a deal with your companion, d o not leave him when there is still any ambiguity (in the deal) between you."'  

كُنْتُ أَبِيعُ الذَّهَبَ بِالْفِضَّةِ أَوِ الْفِضَّةَ بِالذَّهَبِ فَأَتَيْتُ رَسُولَ اللَّهِ ﷺ فَأَخْبَرْتُهُ بِذَلِكَ فَقَالَ إِذَا بَايَعْتَ صَاحِبَكَ فَلاَ تُفَارِقْهُ وَبَيْنَكَ وَبَيْنَهُ لَبْسٌ  

he did not like to exchange Dinars for Dirhams or Dirhams for Dinars.  

أَنْ يَأْخُذَ الدَّنَانِيرَ مِنَ الدَّرَاهِمِ وَالدَّرَاهِمَ مِنَ الدَّنَانِيرِ  

he did not see anything wrong with parying Dirhams for Dinars.  

أَنَّهُ كَانَ لاَ يَرَى بَأْسًا يَعْنِي فِي قَبْضِ الدَّرَاهِمِ مِنَ الدَّنَانِيرِ وَالدَّنَانِيرِ مِنَ الدَّرَاهِمِ  

he disliked it (this transaction) if it was done on credit. (Da 'if )  

عَنْ إِبْرَاهِيمَ فِي قَبْضِ الدَّنَانِيرِ مِنَ الدَّرَاهِمِ أَنَّهُ كَانَ يَكْرَهُهَا إِذَا كَانَ مِنْ قَرْضٍ  

he did not see anything wrong with it even if it was on credit.  

أَنَّهُ كَانَ لاَ يَرَى بَأْسًا وَإِنْ كَانَ مِنْ قَرْضٍ  

This is what I have found on this topic.  

أَبُو عَبْدِ الرَّحْمَنِ كَذَا وَجَدْتُهُ فِي هَذَا الْمَوْضِعِ