The Messenger of Allah ﷺ arrived in Madinah, and the people were paying in advance for dates to be delivered after one or two years, or he said two or three years. He said, "Whoever pays in advance for dates must do so for a known measure and a known weight."
حدثني إسماعيل بن إبراهيم حدثنا ابن أبي نجيح عن عبد الله بن كثير عن أبي المنهال
قدم رسول الله ﷺ المدينة والناس يسلفون في التمر العام والعامين أو قال عامين والثلاثة فقال من سلف في تمر فليسلف في كيل معلوم ووزن معلوم
Its chain is sahih. Abdullah bin Kathir Dari Makki was one of the seven well-known reciters of the Quran, was eloquent in reciting it, and is trustworthy. Abu Minhal is Abdul-Rahman bin Mutim Banani, with the ba pronounced with a damma and the nun unshaddaded, a man of Basra who settled in Makkah, and he is a trustworthy successor. The hadith was narrated by the group, as in al-Muntaqa 2957 and Dhakhair al-Mawarith 2856.Salaf, as given in al-Nihayah, one says "salafat" and "aslafat taslifan wa islafan," and the noun is "salaf." In transactions it has two meanings. The first is a loan that carries no benefit for the lender other than reward and gratitude, and the borrower is obliged to return it just as he took it, and the Arabs call a loan "salaf." The second is that one gives money for goods to be delivered at a fixed future date at a price advantageous compared to the price prevailing at the time of the advance, which is a benefit for the one advancing the money, and this is called "salam," unlike the first. What is meant in the hadith is the second meaning, namely salam. This will come again at 1937 and 2548.