Indian Contract Act, 1872
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.
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.