The Messenger of Allah ﷺ forbade selling palm-trees till the dates began to ripen, and ears of corn till they were white and were safe from blight, forbidding it both to the buyer and to the seller. (Using translation from Abū Dāʾūd 3368)  

أَنَّ رَسُولَ اللهِ ﷺ نَهَى عَنْ بَيْعِ النَّخْلِ حَتَّى يَزْهُوَ وَعَنِ السُّنْبُلِ حَتَّى يَبْيَضَّ وَيَأْمَنَ الْعَاهَةَ نَهَى الْبَائِعَ وَالْمُشْتَرِيَ  

a man form among the companions of the Prophet told him, he said: "O Messenger of Allah we cannot buy Saihani dates or 'idhq dates for the same amount of mixed dates (which are of inferior quality). Should we increase (the amount we give in payment for the better quality dates)?" The messenger of Allah said: "Sell them for silver them buy with it" (Using translation from Nasāʾī 4552)  

أَنَّ رَجُلًا مِنْ أَصْحَابِ النَّبِيِّ ﷺ أَخْبَرَهُ قَالَ يَا رَسُولَ اللهِ إِنَّا لَا نَجْدُ الصَّيْحَانِيَّ وَلَا الْعِذْقَ بِجَمْعِ التَّمْرِ حَتَّى نَزِيدَهُمْ فَقَالَ رَسُولُ اللهِ ﷺ «بِعْهُ بِالْوَرِقِ ثُمَّ اشْتَرِهِ»