What did the Prophet Muhammad (saw) forbid when gold and silver were not used for renting land?
 Narrated Rafi` bin Khadij:                     We worked on farms more than anybody else in Medina. We used to rent the land at the yield of specific delimited portion of it to be given to the landlord. Sometimes the vegetation of that portion was affected by blights etc., while the rest remained safe and vice versa, so the Prophet forbade this practice. At that time gold or silver were not used (for renting the land). If they provided the seeds, they would get so-and-so much.