Section 21 in The Transfer of Property Act, 1882
Title: Contingent interest.
Where, on a transfer of property, an interest therein is created in favour of a person to take effect only on the happening of a specified uncertain event, or if a specified uncertain event shall not happen, such person thereby acquires a contingent interest in the property. Such interest becomes a vested interest, in the former case, on the happening of the event, in the latter, when the happening of the event becomes impossible.
Exception.-- Where, under a transfer of property, a person becomes entitled to an interest therein upon attaining a particular age, and the transferor also gives to him absolutely the income to arise from such interest before he reaches that age, or directs the income or so much thereof as may be necessary to be applied for his benefit, such interest is not contingent.
Title: Transfer to members of a class who attain a particular age.
Where, on a transfer of property, an interest therein is created in favour of such members only of a class as shall attain a particular age, such interest does not vest in any member of the class who has not attained that age.
Title: Transfer contingent on happening of specified uncertain event.
Where, on a transfer of property, an interest therein is to accrue to a specified person if a specified uncertain event shall happen, and no time is mentioned for the occurrence of that event, the interest fails unless such event happens before, or at the same time as, the intermediate or precedent interest ceases to exist.
Title: Transfer to such of certain persons as survive at some period not specified.
Where, on a transfer of property, an interest therein is to accrue to such of certain persons as shall be surviving at some period, but the exact period is not specified, the interest shall go to such of them as shall be alive when the intermediate or precedent interest ceases to exist, unless a contrary intention appears from the terms of the transfer.
A transfers property to B for life, and after his death to C and D, equally to be divided between them, or to the survivor of them. C dies during the life of B. D survives B. At B's death the property passes to D.
Title: Conditional transfer.
An interest created on a transfer of property and dependent upon a condition fails if the fulfilment of the condition is impossible, or is forbidden by law, or is of such a nature that, if permitted, it would defeat the provisions of any law, or is fraudulent, or involves or implies injury to the person or property of another, or the Court regards it as immoral or opposed to public policy.
(a) lets a farm to B on condition that he shall walk a hundred miles in an hour. The lease is void.
(b) A gives Rs. 500 to B on condition that he shall marry A's daughter C. At the date of the transfer C was dead. The transfer is void.
(c) A transfers Rs. 500 to B or. condition that she shall murder C. The transfer is void.
(d) A transfer Rs. 500 to his nece C if she will desert her husband. The transfer is void.