'Servant of the Lord' in the Bible

But as for me, justified, I will behold your face; when I awake, your presence will satisfy me. To the Director: By the servant of the LORD, David, who spoke the words of this song to the LORD on the day when the LORD delivered him from the hands of all his enemies and from the hand of Saul.

{To the chief Musician, A Psalm of David, the servant of the LORD, who spake unto the LORD the words of this song in the day that the LORD delivered him from the hand of all his enemies, and from the hand of Saul: And he said,} I will love thee, O LORD, my strength.

My tongue will declare your righteousness and praise you all day long. To the Director: By the servant of the LORD, David.

{To the chief Musician, A Psalm of David the servant of the LORD.} The transgression of the wicked saith within my heart, that there is no fear of God before his eyes.