Ibn 'Abbas (Allah be pleased with them) reported that when Messenger of Allah ﷺ came to (Medina) and the people were paying in advance (for the fruits, etc.), he said to them: He who makes an advance payment should not make advance payment except for a specified measure and weight (and for a specified period).

حَدَّثَنَا شَيْبَانُ بْنُ فَرُّوخَ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنِ ابْنِ أَبِي نَجِيحٍ، حَدَّثَنِي عَبْدُ اللَّهِ، بْنُ كَثِيرٍ عَنْ أَبِي الْمِنْهَالِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ قَدِمَ رَسُولُ اللَّهِ ﷺ وَالنَّاسُ يُسْلِفُونَ فَقَالَ لَهُمْ رَسُولُ اللَّهِ ﷺ " مَنْ أَسْلَفَ فَلاَ يُسْلِفْ إِلاَّ فِي كَيْلٍ مَعْلُومٍ وَوَزْنٍ مَعْلُومٍ " .