This Psalm is almost word for word the same as Psalm 14. From the headings of the Psalms, and in other ways, we know that before our present Book of 150 Psalms existed, there were several smaller collections, just as we today have different collections of hymns and Christian songs. There was a "David" collection, a "Korah" collection, and a collection of the "Leader". This Psalm would have been in two different collections. Apart from a few smaller differences between this Psalm and Psalm 14, there is a different name used for God (see Note 2 below), and verse 5 in this Psalm is quite different from Psalm 14.
It seems likely that while Psalm 14 applied to those in Israel who gave no thought to God in their lives, Psalm 53 applies a similar message to those of other nations who threatened Israel - but did not succeed. In spite of the boasted power of such people, terror and panic struck them and many perished in battle. The Psalm as a whole tells us what happens in the lives and to the lives of those who reject God. In this way it applies strongly to any of us anywhere if we try to live our lives as though God did not exist.
When people turn away from God and in effect say, "There is no God", then there is nothing to stop their lives becoming more and more evil. They become "corrupt, they commit abominable acts". The life of every nation and society illustrates this. They become "perverse", and have no desire at all for what is good. They also become oppressors of others. The Lord is concerned for all human beings as his creatures, and in righteous anger he says, "they eat up my people as they eat bread". (See the similar way that oppression of others is described in Micah 3:1-4.)
God never rejects anyone who turns to him. The word of Jesus is, "anyone who comes to me I will never drive away" (John 6:37). Whatever our sin, if we turn from it and turn back to God, we will always find him willing to accept and forgive us. But those who refuse, and continue to reject him, need to realise that God must reject them. The New Testament has this same solemn warning in Romans 1:18-32. Notice carefully what it says in this Psalm about those who say in their hearts "There is no God', and act as if there was no God to whom they would have to give account for their lives:
a. God sees them. "God looks down from heaven" is the way verse 2 puts it, and he sees the good and evil of every person's life.
b. God speaks to challenge them (verse 4), "Have they no knowledge, those evildoers who -- do not call upon God?"
c. God acts, and they are in terror and panic that they have never known before. They are defeated on the battlefield and there God "scatters the bones of the ungodly" (verse 5). Those who were so proud in their own strength and wisdom are "put to shame". These evil-doers are called "fools" because they have heard and known of God's punishment on evil-doers in the past, and yet continue in the same way themselves.
The psalm ends with a prayer that the people of Israel must often have prayed in times of difficulty. Most of all in the time when they were defeated by Babylon and sent into exile they prayed for deliverance and for God to "restore the fortunes of his people". And God answered that prayer so that they rejoiced and were glad.
Meditation: While those who turn from God face fear and shame, those who trust in him can rejoice even in the midst of difficulties and trials. See Romans 5:1-5.
a. Read 2 Kings 7:1-8 and 19:1-7 and 2 Chronicles 20:1-30 as showing ways in which powerful armies were thrown into panic and God's people found deliverance.
b. What helps to keep Christian people from fear when others around are panicking? Recall the words of Psalm 46 and think of Old Testament and New Testament examples of those who found victory over fear, like Isaiah in 2 Kings 18-19 and the apostle Paul in Acts 27. See also Matthew 10:28-29, John 16:33, Philippians 4:6-7 and 1 John 4:4.