Psalm 143 is the fourth in the sequence of five psalms of David (within the collection of eight) wherein David prays for deliverance from enemies. It is classified as one of the seven penitential psalms (Psalms 6; 32; 38; 51; 102; 130; 143). These psalms have in common an acknowledgment of sin (Psalm 32:5; Psalm 8:18; Psalm 51:2-4; Psalm 130:3) and/or a reference to deserved punishment (Psalm 6:1; Psalm 38:1; Psalm 102:10; Psalm 143:2).

In this psalm, David doesn't acknowledge specific sins but is clearly aware of his own failings, asking to be passed over in judgment. He knows that such judgment would find him guilty, as he, like everyone, has sinned (compare Psalm 143:2; Romans 3:10, Romans 3:23). So he pleads for mercy, basing his appeal on God's faithfulness and righteousness (Psalm 143:1) in dealing with one who is His servant (verse 2; compare verses 11-12).

David further implies that he is unable to withstand judgment given his already-overwhelmed state, crushed to the depths of despair by enemy persecution that brought him seemingly near death (verses 3-4, 7). Although David is probably referring to a human enemy (verse 3) and enemies (verse 12) who have persistently hounded him, he may have in mind as well the spiritual Adversary, Satan the devil, and his demons, who are also associated with darkness and the pit (see Ephesians 6:12; Revelation 20:1-2).

David likens his yearning for God to dry ground that needs rain (verse 6). Interestingly, rain in other passages symbolizes God's Word and teachings (Isaiah 55:6-13; Deuteronomy 32:1-3), the Holy Spirit (Isaiah 44:3-4), righteousness (Hosea 10:12) and the coming of God (Hosea 6:1, Hosea 6:3). David needs all of this. In desperation he cries out for God's immediate intervention. He cannot rely on his own overwhelmed and failing spirit (Psalm 143:4, Psalm 143:7), referring to his weakened strength of mind. He requires the help of God's good Spirit (see verse 10). He needs an understanding of how to go forward (verse 8), rescue from his enemies (verse 9), instruction in righteousness (verse 10), and relief and empowerment (verse 11).

As in the opening of the psalm (verses 1-2), David again bases his plea for help (including justice on enemies) on the fact that he is God's servant (verses 11-12)—stressing here God's hesed, rendered "mercy" (verse 12, NKJV) but also translatable as "loyal love" or "devotion." The point is that God has made promises of steadfast love and help to those who are His servants—even, as verse 11 implies, staking His name, His reputation, on this.