The Prophet ﷺ came to Medina and the people used to pay in advance the price of dates to be delivered within two or three years. He said (to them), "Whoever pays in advance the price of a thing to be delivered later should pay it for a specified measure at specified weight for a specified period."  

قَدِمَ النَّبِيُّ ﷺ الْمَدِينَةَ وَهُمْ يُسْلِفُونَ بِالتَّمْرِ السَّنَتَيْنِ وَالثَّلاَثَ فَقَالَ مَنْ أَسْلَفَ فِي شَىْءٍ فَفِي كَيْلٍ مَعْلُومٍ وَوَزْنٍ مَعْلُومٍ إِلَى أَجَلٍ مَعْلُومٍ  

as above, saying, "He should pay the price in advance for a specified measure and for a specified period."  

وَقَالَ فَلْيُسْلِفْ فِي كَيْلٍ مَعْلُومٍ إِلَى أَجَلٍ مَعْلُومٍ  

The Prophet ﷺ came (to Medina) and he told the people (regarding the payment of money in advance that they should pay it) for a known specified measure and a known specified weight and a known specified period.  

سَمِعْتُ ابْنَ عَبَّاسٍ ؓ يَقُولُ قَدِمَ النَّبِيُّ ﷺ وَقَالَ فِي كَيْلٍ مَعْلُومٍ وَوَزْنٍ مَعْلُومٍ إِلَى أَجَلٍ مَعْلُومٍ  

Muhammad or ʿAbdullah bin Abu Al-Mujalid said, "Abdullah bin Shaddad and Abu Burda differed regarding As-Salam, so they sent me to Ibn Abi ʿAufa and I asked him about it. He replied, 'In the lifetime of Messenger of Allah ﷺ, Abu Bakr and ʿUmar, we used to pay in advance the prices of wheat, barley, dried grapes and dates to be delivered later. I also asked Ibn Abza and he, too, replied as above.' "  

إِنَّا كُنَّا نُسْلِفُ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ وَأَبِي بَكْرٍ وَعُمَرَ فِي الْحِنْطَةِ وَالشَّعِيرِ وَالزَّبِيبِ وَالتَّمْرِ وَسَأَلْتُ ابْنَ أَبْزَى فَقَالَ مِثْلَ ذَلِكَ