It was narrated from Ibn 'Umar that the Messenger of Allah (ﷺ) said:"Do not sell fruits until they have ripened." And he forbade (both) the seller and the purchaser (to engage in such a transaction).
حَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَنْبَأَنَا اللَّيْثُ بْنُ سَعْدٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَ " لاَ تَبِيعُوا الثَّمَرَةَ حَتَّى يَبْدُوَ صَلاَحُهَا " . نَهَى الْبَائِعَ وَالْمُشْتَرِيَ .
IbnMaja
The Chapters on Business Transactions • Hadith 2214