It was narrated from Anas bin Malik that :
the Messenger of Allah ﷺ forbade selling fruits until they have changed the color, and selling grapes until they have turned black, and selling grains until they have hardened.

حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا حَجَّاجٌ، حَدَّثَنَا حَمَّادٌ، عَنْ حُمَيْدٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ رَسُولَ اللَّهِ ـ ﷺ ـ نَهَى عَنْ بَيْعِ الثَّمَرَةِ حَتَّى تَزْهُوَ وَعَنْ بَيْعِ الْعِنَبِ حَتَّى يَسْوَدَّ وَعَنْ بَيْعِ الْحَبِّ حَتَّى يَشْتَدَّ .