Watchman Nee emphasizes the believer's need to understand God's judgment on the flesh, asserting that both sin and righteousness stemming from the flesh are futile and cannot please God. He explains that the flesh is inherently hostile to God and incapable of submitting to His law, leading to spiritual death unless it is committed to the cross. Nee encourages believers to recognize their flesh's untrustworthiness and to rely on the Holy Spirit for true spiritual life, warning against self-righteousness and the dangers of trusting in one's own strength. He highlights the necessity of continuous self-judgment and the importance of the cross in the believer's life to ensure that the flesh remains in its rightful place of death. Ultimately, the sermon calls for a deep understanding of the flesh's nature and a commitment to living by the Spirit, as true spiritual maturity is rooted in acknowledging the flesh's corruption and the need for constant dependence on God.