'Abdur-Rahman bin Abi Bakrah narrated that his father said:
"The Messenger of Allah forbade selling silver for silver and gold for gold, unless it was of equal amounts. And he told us to sell gold for silver however we wanted, and silver for gold however we wanted.
Reported by An-Nasa’i (No. 4578), Al-Bukhari (No. 2182), Muslim (No. 1590a) and Ahmad (No. 19500, 19592).
Abu Bakrah (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) forbade the sale of silver for silver and gold for gold except for equal quantities, and commanded us to buy silver with gold as we desire, and to buy gold with silver as we…
وَعَنْ عُبَادَةَ بْنِ اَلصَّامِتِ - رضى الله عنه - قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ اَلذَّهَبُ بِالذَّهَبِ, وَالْفِضَّةُ بِالْفِضَّةِ, وَالْبُرُّ بِالْبُرِّ, وَالشَّعِيرُ بِالشَّعِيرِ…
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ اَلذَّهَبُ بِالذَّهَبِ وَزْناً بِوَزْنٍ مِثْلًا بِمِثْلٍ، وَالْفِضَّةُ بِالْفِضَّةِ وَزْناً بِوَزْنٍ مِثْلًا بِمِثْلٍ…
"Silver for gold is Riba (usury) unless exchanged on the spot; wheat for wheat is Riba unless exchanged on the spot; barley for barley is Riba unless exchanged on the spot; and dates for dates is Riba unless exchanged on the spot."