Sunan Abi Dawud

Sa’d b. Abi Waqqas reported the Messenger of Allah (May peace be upon him) as saying :If anyone says when he hears the MU’ADHDHIN : “And I testify that there is no god but Allah alone who has no partner and that Muhammad is His servant and Apostle: I am satisfied with Allah as lord, with Muhammad as apostle and with Islam as religion”, he will be forgiven