What does the Bible say about trusting the flesh?

Scripture highlights the deceitfulness of the heart in Jeremiah 17:9, stating that 'the heart is deceitful above all things.' The flesh is represented by Abner in 2 Samuel, who deceives David and represents a betrayal of God's true king. This illustrates the struggle between the spirit and the flesh, emphasizing the importance of relying on God's wisdom rather than our selfish desires. David's initial trust in Abner serves as a warning of the peril in leaning on our own understanding, which ultimately leads to conflict and sin.