The sermon examines the parable of the two sons in Matthew 21, contrasting the son who initially refuses but later obeys with the son who verbally agrees but fails to act. This narrative is used to illustrate that genuine faith requires repentance, defined as turning away from sin, which is the necessary precursor to believing in the gospel. The message emphasizes that lip service to God is insufficient; true discipleship involves aligning one's actions with their words, just as the first son ultimately did. The preacher connects this biblical principle to the historical example of D-Day, where decisive action under authority led to victory, and applies it to the Great Commission. Ultimately, the sermon calls listeners to recognize Jesus' supreme authority and to respond with obedient evangelism, ensuring they are the sons who do the Father's will.