Section 14(1)(c) in The Delhi and Ajmer Rent Control Act, 1952
(c)that the tenant has used the premises for a purpose other than that for which they were let--(i)if the premises have been let on or after the 9th day of June, 1952, without obtaining the consent in writing of the landlord; or(ii)if the premises have been let before the said date without obtaining his consent;