law: Indian Contract Act, 1872 
  25. Agreement without consideration,
  
  void, unless it is in writing and registered or is a promise to compensate for
  
  something done or is a promise to pay a debt barred by limitation law
  An agreement made without consideration is void, unless-
  (1) it is expressed in writing and registered under the law for
  
  the time being in force for the registration of 9[documents], and is
  
  made on account of natural love and affection between parties standing in a
  
  near relation to each other; or unless
  (2) it is a promise to compensate, wholly or in part, a person
  
  who has already voluntarily done something for the promisor, or something which
  
  the promisor was legally compellable to do; or unless
  (3) it is a promise, made in writing and signed by the person to
  
  be charged therewith or by his agent generally or specially authorized in that
  
  behalf, to pay wholly or in part a debt of which the creditor might have
  
  enforced payment but for the law for the limitation of suits.
  In any of these cases, such an agreement is a contract.
   Explanation 1 :  Nothing in this section shall affect
  
  the validity, as between the donor and donee, of any gift actually made.
   Explanation 2:   An agreement to which the consent of
  
  the promisor is freely given is not void merely because the consideration is
  
  inadequate; but the inadequacy of the consideration may be taken into account
  
  by the Court in determining the question whether the consent of the promisor
  
  was freely given.
   Illustrations 
  (a) A promises, for no consideration, to give to B Rs. 1,000.
  
  This. is a void agreement.
  (b) A, for natural love and affection, promise to give his son B,
  
  Rs. 1,000 A puts his promise to B into writing and registers it. This is a
  
  contract.
  (c) A finds B's purse and gives it to him. B promises to give A
  
  Rs. 50. This is a contract.
  (d) A supports, B's infant son. B promises to pay A's expenses
  
  in so doing. This is a contract.
  (e) A owes B Rs. 1,000, but the debt is barred by the Limitation
  
  Act. A signs written promise to pay B Rs. 500 on account of the debt. This is a
  
  contract.
  (f) A agrees to sell a horse worth Rs. 1,000 for Rs. 10. A' s
  
  consent to the agreement was freely given. The agreement is a contract
  
  notwithstanding the inadequacy of the consideration.
  (g) A agrees to sell horse of worth Rs. 1,000 for Rs. 10. A
  
  denies that his consent to the agreement was freely given.
  The inadequacy of the consideration is a fact which the court
  
  should take into account into considering whether or not A' s consent was
  
  freely given.