Muwatta Malik, Book 31, Hadith 1302 (In-Book)

Yahya related to me from Malik from Nafi from Ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, forbade selling fruit until it had started to ripen. He forbade the transaction to both buyer and seller.

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنْ بَيْعِ الثِّمَارِ حَتَّى يَبْدُوَ صَلاَحُهَا نَهَى الْبَائِعَ وَالْمُشْتَرِيَ ‏.‏

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also referenced under: Book 31, Hadith 10 (USC-MSA)