Christians believe that people can be saved and go to heaven if they believe in Jesus and are sorry for their sins. I think the blank check refers to the Christian belief that a person can live a life full of sin but still be saved by Jesus if they make sure to repent before they die. The speaker does not want to stop living an immoral life, but hopes he has a little more time so that he can stop and repent before he dies - thereby cashing Jesus's blank check.
Christians believe that people can be saved and go to heaven if they believe in Jesus and are sorry for their sins. I think the blank check refers to the Christian belief that a person can live a life full of sin but still be saved by Jesus if they make sure to repent before they die. The speaker does not want to stop living an immoral life, but hopes he has a little more time so that he can stop and repent before he dies - thereby cashing Jesus's blank check.