law: Indian Contract Act, 1872 
  69. Reimbursement of person paying
  
  money due by another, in payment of which he is interested
  A person who is interested in the payment of money which another
  
  is bound by law to pay, and who therefore pays it, is entitled to be reimbursed
  
  by the other.
   Illustration 
  B holds land in
  
  Bengal, on a lease granted by A, the zamindar. The revenue payable by A to the
  
  government being in arrears, his land is advertised for sale by the government.
  
  Under the revenue law, the consequence of such sale will be the annulment of
  
  B's lease. B to prevent the sale and the consequent annulment of his one lease,
  
  pays to the government the sum due from A. A is bound to make good to B the
  
  amount so paid.