Sahih Bukhari Volume 005, Book 058, Hadith Number 159.

Narated By Abu Burda : When I came to Medina. I met Abdullah bin Salam. He said, "Will you come to me so that I may serve you with Sawiq (i.e. powdered barley) and dates, and let you enter a (blessed) house that in which the Prophet entered?" Then he added, "You are In a country where the practice of Riba (i.e. usury) is prevalent; so if somebody owe you something and he sends you a present of a load of chopped straw or a load of barley or a load of provender then do not take it, as it is Riba."

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