كتاب البيوع
21  
The Book of Transactions
(14)
Chapter: The prohibition of selling fresh dates in exchange for dry dates except in the case of 'Araya
(14)
باب تَحْرِيمِ بَيْعِ الرُّطَبِ بِالتَّمْرِ إِلاَّ فِي الْعَرَايَا ‏‏
Sahih Muslim 1539 h

Zaid b. Thabit (Allah be pleased with him) reported Allah's Messenger (ﷺ) granting concession in case of 'ariyya transactions and that implies selling of (dry dates for fresh dates) according to a measure.

وَحَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا عُبَيْدُ اللَّهِ، حَدَّثَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنْ زَيْدِ بْنِ ثَابِتٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَخَّصَ فِي الْعَرَايَا أَنْ تُبَاعَ بِخَرْصِهَا كَيْلاً ‏.‏
Reference : Sahih Muslim 1539h
In-book reference : Book 21, Hadith 83
USC-MSA web (English) reference : Book 10, Hadith 3684
  (deprecated numbering scheme)