What does Psalm 40:3 mean?

David was so joyful and appreciative of God's deliverance of him from his enemies that he lifted his voice in a song of praise to the Lord. He shared this praise with his countrymen so that they would reverence the Lord and trust in Him. This "reverence" is the meaning of the term "fear" in passages such as this.

When God delivers sinners from their sin, He draws them out of what seems like a pit (Psalm 40:2). Those who cry to the Lord for salvation and believe on Jesus as Savior are rescued. God gives them a brand–new life (Ephesians 2:4–10; 1 John 3:14). Second Corinthians 5:17 declares that anyone who is in Christ is a new creation. The Lord not only saves them from the pit of sin but also establishes their steps and gives them a new direction in life. Saul of Tarsus found forgiveness and a new life in Christ (Acts 9). He testified in 1 Timothy 1:15–16 that Christ Jesus came into the world to save sinners, of whom he said he was the foremost. But he received mercy in order for Jesus Christ to display His perfect patience as an example to other believers.