Save me, O God, by thy name - The word “name” here may include the perfections or attributes properly implied in the name. It is a calling on God as God, or in view of all that is implied in his name, or that constitutes the idea of “God.” That name would imply all of power and benevolence that was necessary to secure his salvation or safety. The particular object of the prayer here is that God would save him from the design of the Ziphims to betray him to Saul. In some way David seems to have been apprised of the information which they had given to Saul, or at least to have suspected it so strongly that he felt it was necessary for him to move from place to place in order to find safety.
And judqe me by thy strength - The word “judge” here is used in the sense of declaring a judgment in his favor, or of vindicating him. See the notes at Psalms 7:8. Compare Psalms 18:20; Psalms 26:1; Psalms 43:1. The idea is, Vindicate or save me by thy power.

Hear my prayer, O God - My earnest cry for deliverance from the designs of those who would betray me.
Give ear to the words of my mouth - Incline thine ear to me, as one does who wishes to hear. See the notes at Psalms 17:6.

For strangers are risen up against me - That is, foreigners; those of another nation or land. Saul and his friends who sought the life of David were his own countrymen; these persons who sought go betray him were another people. They attempted to gain the favor of Saul, or to secure a reward from him, by betraying to him an innocent man whom he was persecuting.
And oppressors seek after my soul - Seek after my life. The word here rendered “oppressors” means people of violence; the proud; the haughty; persecutors; tyrants. The word properly denotes those who exert their power in an arbitrary manner, or not under the sanction of law.
They have not set God before them - They do not act as in the presence of God. They do not regard his authority. See the notes at Psalms 36:1. The word “Selah” here merely marks a musical pause. It indicates nothing in regard to the sense.

Behold, God is mine helper - That is, God alone can aid me in these circumstances, and to him I confidently look.
The Lord is with them that uphold my soul - My friends; those who have rallied around me to defend me; those who comfort me by their presence; those who sustain me in my cause, and who keep me from sinking under the burden of my accumulated troubles.

He shall reward evil unto mine enemies - Margin, “those that observe me.” The original word here means literally “to twist, to twist together;” then, to press together; then, to “oppress,” or to treat as an enemy. The reference here is to those who pressed upon him as enemies, or who endeavored to crush him. The idea is that God would recompense them for this conduct, or that he would deal with them as they deserved.
Cut them off in thy truth - In thy faithfulness; in thy regard for what is right. This is simply a prayer, or an expression of strong confidence, that God would deal with them as they deserved, or that he would not suffer such conduct to pass without a proper expression of his sense of the wrong. There is no evidence that David in this prayer was prompted by private or vindictive feeling.

I will freely sacrifice unto thee - The Hebrew words rendered “freely,” mean with “willingness, voluntariness, spontaneousness.” The idea is, that he would do it of a free or willing mind; without constraint or compulsion; voluntarily. The reference is to a free-will or voluntary offering, as distinguished from one, that was prescribed by law. See Exodus 35:29; Exodus 36:3; Leviticus 7:16; Leviticus 22:18; Numbers 15:3; Numbers 29:39. The idea is, that as the result of the divine interposition which he prayed for, he would bring voluntary offerings to God in acknowledgment of his goodness and mercy.
I will praise thy name, O Lord - I will praise thee. See Psalms 52:9.
For it is good - That is, God himself is benevolent; and David says that he would express his sense of God’s goodness by offering him praise.

For he hath delivered me out of all trouble - This is spoken either in confident expectation of what would be, or as the statement of a general truth that God did deliver him from all trouble. It was what he had experienced in his past life; it was what he confidently expected in all time to come.
And mine eye hath seen his desire upon mine enemies - The words “his desire” are not in the original. A literal translation would be, “And on my enemies hath my eye looked.” The meaning is, that they had been overthrown; they had been unsuccessful in their malignant attempts against him; and he had had the satisfaction of “seeing” them thus discomfited. Their overthrow had not merely been reported to him, but he had had ocular demonstration of its reality. This is not the expression of malice, but of certainty. The fact on which the eye of the psalmist rested was his own safety. Of that he was assured by what he had witnessed with his own eyes; and in that fact he rejoiced. There is no more reason to charge malignity in this case on David, or to suppose that he rejoiced in the destruction of his enemies as such, than there is in our own case when we are rescued from impending danger. It is proper for Americans to rejoice in their freedom, and to give thanks to God for it; nor, in doing this, is it to be supposed that there is a malicious pleasure in the fact that in the accomplishment of this thousands of British soldiers were slain, or that thousands of women and children as the result of their discomfiture were made widows and orphans. We can be thankful for the mercies which we enjoy without having any malignant delight in those woes of others through which our blessings may have come upon us.