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 ﷺ ـ قَالَ " لاَ تَبِيعُوا الثَّمَرَةَ حَتَّى يَبْدُوَ صَلاَحُهَا " . نَهَى الْبَائِعَ وَالْمُشْتَرِيَ .