law: Indian Contract Act, 1872 
  10. What agreements are contracts 
  All agreements are contracts if they are made by the free
  
  consent of parties competent to contract, for a lawful consideration and with a
  
  lawful object, and are not hereby expressly declared to be void.
  Nothing herein contained shall affect any law in force in 3[India],
  
  and not hereby expressly repealed, by which any contract is required to be made
  
  in writing  or in the presence of witnesses, or any law
  
  relating to the registration of documents.