The Catechism in Questions & Answers

241. What is the task of the believer?

Human beings are called upon to accept God’s word, trust in it, and act in accordance with it. Jesus Christ demanded: “You believe in God, believe also in Me” (John 14: 1). He promised that “whoever believes in Him should not perish but have everlasting life” (John 3: 16). He also emphasised the consequence of unbelief in all its implications: “For if you do not believe that I am He, you will die in your sins” (John 8: 24).

“So then faith comes by hearing, and hearing by the word of God.”
Romans 10: 17