The God of my mercy will prevent me In the Hebrew, there is the affix of the third person, but we have the point which denotes the first. [1] The Septuagint has adopted the third person, and Augustine too ingeniously, though with a good design, has repeatedly quoted the passage against the Pelagians, in proof that the grace of God is antecedent to all human merit. In the same manner, he has again and again cited the preceding verse, to refute the arrogancy of those who boast of the power of free-will. "I will put in trust my strength with thee," he says; "that is, men must subject themselves with all modesty and humility to God, as having no strength but that with which he supplies them." Now, it may be said with great plausibility, that the man puts his strength in trust with God, who declares that he has no strength but what comes from him, and who depends entirely upon his help. The sentiment inculcated is also, without all doubt, a pious and instructive one; but we must be ever on our guard against wresting Scripture from its natural meaning. The Hebrew word qdm, kidem, means no more than to come forward seasonably; and David simply intimates that the divine assistance would be promptly and opportunely extended. [2] The scope of the words is, that God will interpose at the very moment when it is required, however much he may retard or defer his assistance. Were it not that we are hurried on by the excessive eagerness of our own wishes, we would sufficiently recognize the promptness with which God hastens to our help, but our own precipitance makes us imagine that he is dilatory. To confirm his faith, he calls him the God of his mercy, having often proved him to be merciful; and the experience of the past afforded him good hopes of what he might expect in the future. The idea of some, that David uses the word in an active sense, and praises his own mercy, is poor and unnatural. Its passive use is quite common.

Footnotes

1 - "We have chsdv, his mercy, with the points chsdy, my mercy, the keri being for the one, and the kethib for the other. And, accordingly, of the interpreters, some read the one, some the other, both certainly meaning the same thing: the Chaldee, the God of my grace, or goodness, or mercy;' but the LXX. O Theos mou to eleos autou,' My God his mercy,' and so the Latin." -- Hammond Green translates, "My God shall prevent me with his loving-kindness."

2 - Horsley reads, "God shall give me ready help."

The God of my mercy shall prevent me - Or rather, "My God - his mercy shall prevent me." This is in accordance with the present reading of the Hebrew text, and is probably correct. The psalmist looks to God as his God, and then the feeling at once springs up that his mercy - favor - his loving-kindness - "would" "prevent" him. On the word "prevent" see the notes at Psalm 21:3; compare Psalm 17:13; Psalm 18:5. The meaning here is, that God would "go before him," or would "anticipate" his necessities.
God shall let me see my desire upon mine enemies - That is, He will let me see them discomfited, and disappointed in their plans. This is equivalent to saying that God would give him the victory, or would not suffer them to triumph over him. See the notes at Psalm 54:7.

The God of my mercy shall prevent me - The mercy of God shall go before me, and thus help me in all my doings.
God shall let me see my desire - The sentence is short. God will let me see concerning my enemies, i.e., how he will treat them.

The God of my mercy shall (h) prevent me: God shall let me see [my desire] upon mine enemies.
(h) He will not fail to help me when need requires.

The God of my mercy shall prevent me,.... Or "of my grace", or "goodness", as the Targum; see 1-Peter 5:10. God is gracious in himself, and he has treasured up a fulness of grace in Christ: he is the donor of all the blessings of grace in the covenant; and the author of all internal grace in the hearts of his people; and who supplies them with more grace as they want it; and he is the Father of all temporal and spiritual mercies. The "Cetib", or writing, is "his mercy"; the "Keri", or reading, is "my mercy"; grace or mercy is the Lord's; it is his own, which he disposes of as he pleases; being given and applied, it is the believer's; all the grace and mercy in the heart of God, in his Son, and in his covenant, is the saints', which he keeps for them with Christ for evermore; "the God of my mercy", or "grace", is the same with "my merciful", or "my gracious God"; who goes before his people, as he does the Messiah, with the blessings of his goodness, Psalm 21:3. It may be rendered, "hath came before me"; and denote the antiquity of his love, being before his people's to him, and the early provisions of his grace and mercy for them: or "doth prevent me": expressing the freeness of it; he not waiting for any duties, services, or conditions to be performed, but bestows his grace and mercy, notwithstanding much unworthiness: or "shall come before me"; designing the seasonable and timely application of mercy come before his fears, as it sometimes does the prayers of his people, Isaiah 65:24;
God shall let me see my desire upon mine enemies; expressed in the following verses, Psalm 59:11; or "vengeance upon them"; as the Targum paraphrases it; see Psalm 58:10.

prevent me-- (Psalm 21:3).
see my desire--in their overthrow (Psalm 54:7).
enemies--as in Psalm 5:8.

In this second half of the Psalm the cry of fear is hushed. Hope reigns, and anger burns more fiercely. The Ker says that Psalm 59:11 is to be read: אלהי חסדּי יקדּמני, my gracious God will anticipate me, - but with what? This question altogether disappears if we retain the Chethb and point אלהי הסדּו: my God will anticipate me with His mercy (cf. Psalm 21:4), i.e., will meet me bringing His mercy without any effort of mine. Even the old translators have felt that chcdw must belong to the verb as a second object. The lxx is perfectly correct in its rendering, ὁ Θεὸς μου τὸ ἔλεος αὐτοῦ προφθάσει με. The Ker has come into existence in looking to v. 18, according to which it seems as though אלהי הסדּי ought to be added to the refrain, Psalm 59:10 (cf. a similar instance in Psalm 42:6-7). But Psalm 59:11 would be stunted by doing this, and it accords with Biblical poetic usage that the refrain in v. 18 should be climactic in comparison with Psalm 59:10 (just as it also does not altogether harmonize in its first half); so that Olshausen's proposal to close Psalm 59:10 with אלהי חסדי and to begin Psalm 59:11 with חסדו (cf. Psalm 79:8) is only just to be put on record. The prayer "slay them not" does not contradict the prayer that follows for their destruction. The poet wishes that those who lie in wait for him, before they are totally swept away, may remain for a season before the eyes of this people as an example of punishment. In accordance with this, הניעמו, by a comparison of the Hiph. in Numbers 32:13, and of the Kal in Psalm 59:16, Psalm 109:10, is to be rendered: cause them to wander about (Targum, cf. Genesis Rabba, ch. 38 init., טלטלמו); and in connection with בחילך one is involuntarily reminded of Psalm 10:10, Psalm 10:14, and is tempted to read בחלך or בחלך: cause them to wander about in adversity or wretchedness, = Arab. ‛umr ḥâlik, vita caliginosa h. e. misera), and more especially since בחילך occurs nowhere else instead of בּזרעך or בּימינך. But the Jod in בחילך is unfavourable to this supposition; and since the martial apostrophe of God by "our shield" follows, the choice of the word is explained by the consideration that the poet conceives of the power of God as an army (Joel 2:25), and perhaps thinks directly of the heavenly host (Joel 3:11), over which the Lord of Hosts holds command (Hitzig). By means of this He is first of all to cause them to go astray (נע ונד, Genesis 4:12), then utterly to cast them down (Psalm 56:8). The Lord (אדני) is to do this, as truly as He is Israel's shield against all the heathen and all pseudo-Israelites who have become as heathen. The first member of Psalm 59:13 is undoubtedly meant descriptively: "the sin of their mouth (the sin of the tongue) is the word of their lips" (with the dull-toned suffix mo, in the use of which Ps 59 associates itself with the Psalm of the time of Saul, Psalm 56:1-13, Psalm 11:1-7, Psalm 17:1-15, 22, 35, Psalm 64:1-10). The combination ולילּכדוּ בגאונם, however, more readily suggests parallel passages like Proverbs 11:6 than Proverbs 6:2; and moreover the מן of the expression וּמאלה וּמכּחשׁ, which is without example in connection with ספּר, and, taken as expressing the motive (Hupfeld), ought to be joined with some designations of the disposition of mind, is best explained as an appended statement of the reason for which they are to be ensnared, so that consequently יספּרוּ (cf. Psalm 69:27; Psalm 64:6) is an attributive clause; nor is this contrary to the accentuation, if one admits the Munach to be a transformation of Mugrash. It is therefore to be rendered: "let them, then, be taken in their pride, and on account of the curse and deceit which they wilfully utter." If, by virtue of the righteousness of the Ruler of the world, their sin has thus become their fall, then, after they have been as it were a warning example to Israel, God is utterly to remove them out of the way, in order that they (it is unnecessary to suppose any change of subject), while perishing, may perceive that Elohim is Ruler in Jacob (בּ, used elsewhere of the object, e.g., Micah 5:1, is here used of the place of dominion), and as in Jacob, so from thence unto the ends of the earth (ל like על, Psalm 48:11) wields the sceptre. Just like the first group of the first part, this first group of the second part also closes with Sela.
The second group opens like the second group in the first part, but with this exception, that here we read וישׁבוּ, which loosely connects it with what precedes, whereas there it is ישׁוּבוּ. The poet's gaze is again turned towards his present straitened condition, and again the pack of dogs by which Saul is hunting him present themselves to his mind. המּה points towards an antithesis that follows, and which finds its expression in ואני. ויּלינוּ and לבּקר stand in direct contrast to one another, and in addition to this לערב has preceded. The reading of the lxx (Vulgate, Luther, [and authorized version]), καὶ γογγύσουσιν = ויּלּינוּ or ויּלּנוּ, is thereby proved to be erroneous. But if ויּלינוּ is the correct reading, then it follows that we have to take Psalm 59:16 not as foretelling what will take place, but as describing that which is present; so that consequently the fut. consec. (as is frequently the case apart from any historical connection) is only a consecutive continuation of ינוּעוּן (for which the Ker has יניעוּן; the form that was required in Psalm 59:12, but is inadmissible here): they wander up and down (נוּע as in Psalm 109:10, cf. נוּד, Job 15:23) to eat (that is to say, seeking after food); and if they are not satisfied, they pass the night, i.e., remain, eager for food and expecting it, over night on the spot. This interpretation is the most natural, the simplest, and the one that harmonizes best not only with the text before us (the punctuation ישׂבּעוּ, not ישׂבּעוּ, gives the member of the clause the impress of being a protasis), but also with the situation. The poet describes the activity of his enemies, and that by completing or retouching the picture of their comparison to dogs: he himself is the food or prey for which they are so eager, and which they would not willingly allow to escape them, and which they nevertheless cannot get within their grasp. Their morbid desire remains unsatisfied: he, however, in the morning, is able to sing of the power of God, which protects him, and exultantly to praise God's loving-kindness, which satiates and satisfies him (Psalm 90:14); for in the day of fear, which to him is now past, God was his inaccessible stronghold, his unapproachable asylum. To this God, then, even further the play of his harp shall be directed (אזמּרה), just as was his waiting or hoping (אשׁמרה, Psalm 59:10).

Prevent - Thou wilt help me sooner than I expect.