Explanation:

Section 56 ill. (a) of Indian Contract Act, 1872. –

56. Agreement to do impossible act. An agreement to do an act impossible in itself is void. Contract to do act afterwards becoming impossible or unlawful: A contract to do an act which, after the contract is made, becomes impossible or, by reason of some event which the promisor could not prevent, unlawful, becomes void when the act becomes impossible or unlawful. Compensation for loss through nonperformance of act known to be impossible or unlawful: Where one person has promised to be something which he knew or, with reasonable diligence, might have known, and which the promisee did not know to be impossible or unlawful, such promisor must make compensation to such promise for any loss which such promisee sustains through the non-performance of the promise.

Illustrations- (a) A agrees with B to discover treasure by magic. The agreement is void.