What does the Bible say about trusting in God versus relying on the flesh?

In 1 Samuel 20, we see the story of David fleeing from King Saul, who represents the kingdom of the flesh. David's experience illustrates a fundamental truth: the flesh cannot save us, nor can it provide us with true peace. Jonathan warns David that if he returns to Saul's court, he will surely die, signifying that peace cannot be found in the ways of the world. This is echoed in scriptures that remind us of the nature of the flesh, such as Ephesians 2 which describes the world as a course under the prince of the power of the air. Therefore, God separates us from the kingdom of this world, calling us to trust Him alone for salvation and not to look to our own righteousness or efforts. Relying on the flesh ultimately leads to death, while faith in Christ grants us eternal life.