Mishkat al-Masabih 11 Business Transactions كتاب البيوع 78

وَعَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ: نَهَى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْ بَيْعِ الثِّمَارِ حَتَّى يَبْدُوَ صَلَاحُهَا نَهَى الْبَائِعَ وَالْمُشْتَرِي. مُتَّفِقٌ عَلَيْهِ وَفِي رِوَايَةٍ لِمُسْلِمٍ: نَهَى عَنْ بَيْعِ النَّخْلِ حَتَّى تَزْهُوَ وَعَنِ السنبل حَتَّى يبيض ويأمن العاهة

‘Abdallah b. ‘Umar said that God’s Messenger forbade the sale of fruits till they were clearly in good condition, forbidding it both to the seller and to the buyer. A version by Muslim says he forbade selling palm-trees (i.e. their fruit) till the dates began to ripen, and ears of corn till they were white and were safe from blight. (Bukhari and Muslim.)