Section 51. Promisor not bound to perform, unless reciprocal promisee ready and willing to perform.

When a contract consists of reciprocal promises to be simultaneously performed, no promisor need perform his promise unless the promisee is ready and willing to perform his reciprocal promise. Illustrations (a) A and B contract that A shall deliver goods to B to be paid for by B on delivery. A need not deliver the goods, unless B is ready and willing to pay for the goods on delivery. B need not pay for the goods, unless A is ready and willing to deliver them on payment. (b) A and B contract that A shall deliver goods to B at a price to be paid by instalments, the first instalment to be paid on delivery. A need not deliver, unless B is ready and willing to pay the first instalment on delivery. B need not pay the first instalment, unless A is ready and willing to deliver the goods on payment of the first instalment.