Sunan an-Nasai Book 44, Hadith 4565

أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ سُلَيْمَانَ بْنِ عَلِيٍّ، أَنَّ أَبَا الْمُتَوَكِّلِ، مَرَّ بِهِمْ فِي السُّوقِ فَقَامَ إِلَيْهِ قَوْمٌ أَنَا مِنْهُمْ قَالَ قُلْنَا أَتَيْنَاكَ لِنَسْأَلَكَ عَنِ الصَّرْفِ ‏.‏ قَالَ سَمِعْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ قَالَ لَهُ رَجُلٌ مَا بَيْنَكَ وَبَيْنَ رَسُولِ اللَّهِ صلى الله عليه وسلم غَيْرُ أَبِي سَعِيدٍ الْخُدْرِيِّ قَالَ لَيْسَ بَيْنِي وَبَيْنَهُ غَيْرُهُ ‏.‏ قَالَ فَإِنَّ الذَّهَبَ بِالذَّهَبِ وَالْوَرِقَ بِالْوَرِقِ - قَالَ سُلَيْمَانُ أَوْ قَالَ وَالْفِضَّةَ بِالْفِضَّةِ - وَالْبُرَّ بِالْبُرِّ وَالشَّعِيرَ بِالشَّعِيرِ وَالتَّمْرَ بِالتَّمْرِ وَالْمِلْحَ بِالْمِلْحِ سَوَاءً بِسَوَاءٍ فَمَنْ زَادَ عَلَى ذَلِكَ أَوِ ازْدَادَ فَقَدْ أَرْبَى وَالآخِذُ وَالْمُعْطِي فِيهِ سَوَاءٌ ‏.‏

It was narrated from Sulaiman bin Ali:"Abu Al-Mutawakkil passed by them in the market and some people, including me, stood up to greet him. We said: 'We have come to you to ask you about transactions.' He said: 'I heard a man say to Abu Saeed Al-Khudri': 'Is there anyone between you and the Messenger of Allah (in the chain of narrators) apart from Abu Saeed Al-Khudri? He said: 'There is no one else between him and I. He said: Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, salt for salt, equal amounts. Whoever gives more than that or takes more has engaged in Riba, and the taker and the giver are the same