Psalm 54, Deliverance from the Ziphites

For the director of music. With stringed instruments. A maskil of David. When the Ziphites had gone to Saul and said, "Is not David hiding among us?"

This event is most likely that of I Samuel 23: 19-29. (Another similar event with the Ziphites occurs in I Samuel 26.) If Psalms 52, 53 and 54 are ordered by events in David's life, as Kidner suggests, with Psalm 53 representing the dispute with the fool ("nabal") named Nabal in 1 Samuel 25, then this psalm would be based on the events in 1 Samuel 26.

Psalm 54: 1-2, By your name

 Save me, O God, by your name;

vindicate me by your might.

 Hear my prayer, O God;

listen to the words of my mouth.

David opens with a standard plea, "Save me!"  But he relies on God's name (God's character) and then God's might. 

Psalm 54: 3, Evil without regard

 Strangers are attacking me; 

ruthless men seek my life--

men without regard for God.

Selah.

David's plea shifts to an explanation, that strangers are attacking him, men (like Saul and the Ziphites) who have no regard for God. Kidner says that some ancient manuscripts replace the word translated "stranger" with one translated "the insolent" or "the arrogant." This makes more sense in context as neither Saul nor the Ziphites (who were from a town in David's tribe of Judah) are likely to be viewed as strangers.

Psalm 54: 4-5, Let evil recoil

 Surely God is my help;

the Lord is the one who sustains me.

 Let evil recoil on those who slander me;

in your faithfulness destroy them.

After his plea, David returns to the refrain -- God is his help.

Psalm 54: 6-7, Deliverance

 I will sacrifice a freewill offering to you; 

I will praise your name, O LORD, for it is good.

 For he has delivered me from all my troubles, 

and my eyes have looked in triumph on my foes.

A freewill offering is one given without conditions, purely out of thankfulness (Kidner.)  In the final verses, David is safe and celebrating his deliverance.