حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنِ ابْنِ أَبِي نَجِيحٍ، عَنْ عَبْدِ اللَّهِ بْنِ كَثِيرٍ، عَنْ أَبِي الْمِنْهَالِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ قَدِمَ النَّبِيُّ ـ صلى الله عليه وسلم ـ وَهُمْ يُسْلِفُونَ فِي التَّمْرِ السَّنَتَيْنِ وَالثَّلاَثَ فَقَالَ ‏"‏ مَنْ أَسْلَفَ فِي تَمْرٍ فَلْيُسْلِفْ فِي كَيْلٍ مَعْلُومٍ وَوَزْنٍ مَعْلُومٍ إِلَى أَجَلٍ مَعْلُومٍ ‏"‏ ‏.‏

It was narrated that Ibn 'Abbas said: "When the Prophet (PBUH) came (to Al-Madinah), they used to pay in advance for dates, two or three years in advance. He said: 'Whoever pays in advance for dates, let him pay for a known amount or a known weight, to be delivered at a known time.’” Translation Not Available

Book Ref: Sunan Ibn Majah Book 12 Hadith 2280
Web Ref:  Sunan Ibn Majah Vol 3 Book 12 Hadith 2280