Al-Muwatta Hadith 31.71

Malik said, "The generally agreed on way of doing things among us about whatever is weighed but is not gold or silver, i.e. copper, brass, lead, black lead, iron, herbs, figs, cotton, and any such things that are weighed, is that there is no harm in bartering all those sorts of things two for one, hand to hand. There is no harm in taking a ritl of iron for two ritls of iron, and a ritl of brass for two ritls of brass." Malik said, "There is no good in two for one of one sort with delayed terms. There is no harm in taking two of one sort for one of another on delayed terms, if the two sorts are clearly different. If both sorts resemble each other but their names are different, like lead and black lead, brass and yellow brass, I disapprove of taking two of one sort for one of the other on delayed terms." Malik said, "When buying something of this nature, there is no harm in selling It beforetaking possession of it to some one other than the person from whom it was purchased, if the price is taken immediately and if it was bought originally by measure or weight. If it was bought without measuring, it should be sold to someone other than the person from whom it was bought, for cash or with delayed terms. That is because goods have to be guaranteed when they are bought without measuring, and they cannot be guaranteed when bought by weight until they are weighed and the deal is completed. This is the best of what I have heard about all these things. It is what people continue to do among us." Malik said, "The way of doing things among us with what is measured or weighed of things which are not eaten or drunk, like safflower, date-stones, fodder leaves, indigo dye and the like of that is that there is no harm in bartering all those sort of things two for one, hand to hand. Do not take two for one from the same variety with delayed terms. If the types are clearly different, there is no harm in taking two of one for one of the other with delayed terms. There is no harm in selling whatever is purchased of all these sorts, before taking delivery of them if the price is taken from someone other than the person from whom they were purchased." Malik said, "Anything of any variety that profits people, like gravel and gypsum, one quantity of them for two of its like with delayed terms is usury. One quantity of both of them for its equal plus any increase with delayed terms, is usury."