The sermon explores the story of Cain and Abel to illustrate the necessity of atonement and the difference between works-based righteousness and faith-based worship. Drawing parallels to Jesus' parables and the Heidelberg Catechism, it emphasizes that human efforts alone are insufficient to earn God's favor, highlighting Abel's sacrifice as rooted in faith and atonement, contrasting with Cain's offering which lacked this essential element. Ultimately, the message calls for attentive self-reflection on sin, faithful adherence to God's word, and a complete offering of one's life as a living sacrifice, recognizing God's grace and seeking to glorify Him in all aspects of life.