Shari’ah refers to the entire religion of Islam, which Allah chose for His slaves, to lead them forth from the depths of darkness to the light.

Shirk means ascribing a partner or rival to Allah in Lordship (rububiyyah), worship or in His names and attributes. See the detailed answer to know more about the difference between major and minor shirk.

It is not permissible for a Muslim to say “Jesus!” when he is astonished or amazed or startled, as the Christians do, because what they mean when they say it is “Oh my God!”, because they believe that Jesus (‘Eesa – peace be upon him) is God, but Jesus is not God; rather he is the slave and Messenger of Allah. Whoever believes that ‘Eesa is in any way divine is a disbeliever.