Abu Dawud Book 16, Hadith Number 3387.

Narated By Rafi’ ibn Khadij : Hanzalah ibn Qays said that he asked Rafi’ ibn Khadij about the lease of land. He replied: The Apostle of Allah (PBUH) forbade the leasing of land. I asked: (Did he forbid) for gold and silver (i.e. dinars and dirhams)? He replied: If it is against gold and silver, then there is no harm in it.