Sahih al-Bukhari 2170
Narrated Ibn `Umar:
The Prophet (ﷺ) said, "The selling of wheat for wheat is Riba (usury) except if it is handed from hand to 
hand and equal in amount. Similarly the selling of barley for barley, is Riba except if it is from hand to 
hand and equal in amount, and dates for dates is usury except if it is from hand to hand and equal in 
amount. (See Riba-Fadl in the glossary).
حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا اللَّيْثُ، عَنِ ابْنِ شِهَابٍ، عَنْ مَالِكِ بْنِ أَوْسٍ، سَمِعَ عُمَرَ ـ رضى الله عنهما ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ الْبُرُّ بِالْبُرِّ رِبًا إِلاَّ هَاءَ وَهَاءَ، وَالشَّعِيرُ بِالشَّعِيرِ رِبًا إِلاَّ هَاءَ وَهَاءَ، وَالتَّمْرُ بِالتَّمْرِ رِبًا إِلاَّ هَاءَ وَهَاءَ ‏"‏‏.‏