25. A contracts for the sale or letting of property, whether moveable or immoveable, cannot be specifically enforced in favour of a vendor or lessor-(a) who, knowing himself not to have any title to the property, has contracted to sell or let the same;(b) who, though he entered into the contract believing that he had a good title to the property, cannot, at the time fixed by the parties or by the Court for the completion of the sale or letting, give the purchaser or lessee a title free from reasonable doubt;(c) who, previous to entering into the contract, has made a settlement (though not founded on any valuable consideration) of the subject-matter of the contract.Illustrations (a) A, without C's authority, contracts to sell to B an estate which A knows to belong to C. A cannot enforce specific performance of this contract, even though C is willing to confirm it. (b) A bequeaths his land to trustees, declaring that they may sell it with the consent in writing of B. B gives a general prospective assent in writing to any sale which the trustees may make. The trustees then enter into a contract with C to sell him the land. C refuses to carry out the contract. The trustees cannot specifically enforce this contract, as, in the absence of B's consent to the particular sale to C, the title which they can give C is, as the law stands not free from reasonable doubt. (c) A, being in possession of certain land, contracts to sell it to Z. On inquiry it turns out that A claims the land as heir of B, who left the country several years before, and is generally believed to be dead, but of whose death there is no sufficient proof. A cannot compel Z specifically to perform the contract. (d) A, out of natural love and affection, makes a settlement of certain property on his brothers and their issue, and afterwards enters into a contract to sell property to a stranger. A cannot enforce specific performance of this contract so as to override the settlement, and thus prejudice the interest of the persons claiming under it.