Psalm 140 is a prayer for deliverance and protection. David found himself surrounded by people seeking his harm. But rather than devising plans to counter their schemes, he turned to the Lord his Deliverer and cried out to Him for help.
Like all effective prayer, Psalm 140 has its foundation in a solid understanding of the character of God. God hates evil and cares for the poor and afflicted, the weak and needy (Pro 14:31). God is a just God who will not let evil go unpunished. And God loves the upright and has promised that they shall dwell in His presence (Psa 15:1,2). Knowing God is an essential part of effective prayer, because God promises to hear prayers prayed according to His will (1 Jon 5:14).
God is a God who Protects (v. 1-5)
We live in a fallen world among fallen people. As we grow older and see more of the real world, we realise that there are many selfish and unkind people around us, and we cannot always get away from them. They may have no reservations about slandering our character or backstabbing us. They may have no qualms about causing us physical, financial or emotional harm either out of mischief or in order to gain an upper hand. They may ruin our reputation and relationships and care less about us losing our friends and jobs, and their schemes are not always easy to detect.
It becomes hard to trust people in a cruel world, and there is great temptation to fight back and try to outwit them at their own game. We are pressured to find ways to protect ourselves, and are sometimes tempted to pay them back in kind. We may even rationalize that we would be justified when we gossip about them or fight back.
God is not honoured when we seek revenge. Neither is He able to glorify Himself through us when we depend on ourselves rather than Him (2Ch 16:7-9). God is eager to show Himself strong on behalf of those who trust Him, but that means we must trust Him completely instead of depending on our own strength and wits.
God is a God of Justice (v. 6-11)
David knew that God is a God of justice, and justice has to repay evil. But David did not take justice into his own hands. Instead he took his complaint to the Lord who alone is Sovereign over all things. And so should we.
David prayed that the wicked would not succeed in their schemes. If they did, they would become proud and go on to do greater evil. If God gave the wicked success in their plans, it would bring His character to question. Thus in a sense David was asking the Lord to show His righteousness by bringing retribution upon evildoers.
God has said, "Vengeance is mine. I will repay" (Rom 12:19). Giving God His right to judge the wicked means taking our hands off the matter and leaving it completely in His. God is more passionate about justice than we are, and His justice is fairer than ours. Yet God is also a God of mercy, and if He forgives the sinner, let us not be like Jonah who refused to have compassion on Nineveh (Jon 4), because God also had compassion on us.
God is a God of Compassion (v. 12-13)
David was a shepherd and he knew God as a Shepherd who cares for His sheep. When Jesus was on earth, He "was moved with compassion on them, because they fainted, and were scattered abroad, as sheep having no shepherd" (Mat 9:36). God has a place in His heart for the harassed, the weak and the needy. David had a deep confidence in God's care for these people.
We worship a compassionate God. He does not look upon our troubles and afflictions with apathy or indifference. He fights for those who are unable to fight for themselves. He knows what it is like to suffer. Jesus was tempted and tested in every way, yet without sin (Heb 4:15). He was slandered, falsely accused, beaten, abandoned and condemned by people He loved. If there is anyone who understands affliction, it is Jesus, and we can trust Him to come to our aid when we suffer the same. This deep conviction of the compassion of Christ helps us to respond to adversity with confidence and character.