Hadith 7:91
Narrated Ibn 'Abbas (RA):
When the Prophet (ﷺ) came to al-Madinah, they were paying one and two years in advance for fruits. So he (ﷺ) said: "Those who paid in advance for fruits must do so for a specified measurement and weight, and for a specified time." [Agreed upon].
عَنِ اِبْنِ عَبَّاسٍ -رَضِيَ اَللَّهُ عَنْهُمَا- قَالَ: قَدِمَ اَلنَّبِيُّ - صلى الله عليه وسلم -اَلْمَدِينَةَ, وَهُمْ يُسْلِفُونَ فِي اَلثِّمَارِ اَلسَّنَةَ وَالسَّنَتَيْنِ, فَقَالَ: { مَنْ أَسْلَفَ فِي تَمْرٍ فَلْيُسْلِفْ فِي كَيْلٍ مَعْلُومٍ, وَوَزْنٍ مَعْلُومٍ, إِلَى أَجَلٍ مَعْلُومٍ } مُتَّفَقٌ عَلَيْهِ