This sermon examines Paul's argument in Galatians 4, where he uses the historical narrative of Abraham's two sons, Ishmael and Isaac, to illustrate the incompatibility of the Old and New Covenants. The central message is that believers are children of promise and grace, not of the flesh or the law, and therefore must not mix the freedom of the Gospel with the bondage of Mosaic requirements. The exposition highlights how the Old Testament narratives, including the Passover and the Tabernacle, point forward to Christ, demonstrating that the Law serves to reveal sin while the Gospel provides the remedy. The tone is instructional and convicting, urging the audience to recognize that justification is entirely by God's grace through faith, without any merit from human effort or adherence to the Old Covenant. The sermon concludes with a strong exhortation to stand fast in the liberty secured by Christ Jesus and to reject any teaching that suggests additional works are necessary for salvation.