No person shall obstruct or molest any person authorised or empoweredProhibition of

by or under this Act or any person with whom the Corporation or the Commissionerobstruction or molestation in has lawfully contracted, in the execution of his duty or of anything which he isexecution of work. authorised or empowered or required to do by virtue or in consequence of any of the provisions of this Act or any bye-law made thereunder, or in fulfillment of his contract, as the case may be.