Why do Muslims believe the Shahadah is the key to Paradise?

Muslims believe the Shahadah is the key to Paradise because it reassures their salvation. The belief reinforced daily in Muslim’s lives, “There is no God but Allah and Muhammed his Prophet (And Ali is the friend of God,” ensures they receive salvation by accepting Allah in their lives consistently. Each time they believe the statement they say they ensure their salvation and therefore entrance into Paradise. Therefore Muslims believe the Shahadah is the key to Paradise because it ensures salvation.