What does Psalm 3:1 mean?

David laments to the Lord that his enemies are numerous and increasing in their power against him. These formidable enemies had joined David's son Absalom in a rebellion against David. Second Samuel 15:1–6 tells how Absalom stole the hearts of the men of Israel. With a substantial number of supporters, Absalom conspired against his father, King David. Upon hearing about the conspiracy, David and his servants fled from Jerusalem. David had become a fugitive in the wilderness as he was pursued by Absalom's military followers.

Second Samuel 17:1–3 tells us Ahithophel counseled Absalom to allow him to take 12,000 men to pursue David until David became tired and discouraged. Then they would strike David and return David's men to Absalom. This plan, Ahithophel said, would bring peace to Israel. Verse 4 informs us that this "advice seemed right in the eyes of Absalom and all the elders of Israel." Fortunately for David, his ally, Hushai, intervened and convinced Absalom to delay his attack, then warned David (2 Samuel 17:15–16).

This threat of pursuit, by thousands of determined enemies, is the background of David's plea in the psalm.