Indian Contract Act, 1872
Where one man makes a contract with another, neither knowing nor having reasonable ground to suspect that the other is an agent, the principal, if he requires the performance of the contract, can only obtain such performance subject to the right and obligations subsisting between the agent and the other party of the contract.
A, who owes 500 rupees to B, sells, 1,000 rupees worth of rice to B. A is acting as agent for C in the transaction, but B has no knowledge nor reasonable ground of suspicion that such is the case. C cannot compel B to take the rice without allowing him to set-off A's debt.