And I will beat down his foes before his face - I will crush them, or destroy them: showing that the power of doing this was not his own, but was the power of God exerted in his behalf.
And plague them that hate him - His enemies. I will bring "plagues" upon them: calamities, judgments, afflictions. The word is commonly used to denote those judgments which come directly from the hand of God - as famine, pestilence, wasting sickness, the plague, or the "plagues" of Egypt. Exodus 12:13; Exodus 30:12; Numbers 8:19; Numbers 17:11-12. These are all in the hand of God, and can be employed at his pleasure, as storms and tempests may be, in executing his purposes.

And I will (s) beat down his foes before his face, and plague them that hate him.
(s) Though there will always be enemies against God's kingdom yet he promises to overcome them.

And I will beat down his foes before his face,.... In Judea, and in the Gentile world; more especially in Rome Pagan, and Rome Papal; in the most public manner, before his Gospel, and the ministry of it by his servants; and they shall either submit unto it, or be broken to pieces as a potter's vessel; for he must reign till all enemies are put under his feet, 1-Corinthians 15:25,
and plague them that hate him; that would not have him to reign over them, the unbelieving Jews, and all the followers of antichrist; who are either plagued with the judgments of God here, or with everlasting punishment hereafter, with which they will be tormented for ever and ever, Luke 19:14 or "strike" (d) them with a rod of iron, with his wrath and vengeance; strike them down to the ground, and to the lowest hell.
(d) "percutiam", Pagninus, Montanus, Musculus, Piscator, Michaelis.

What is promised in Psalm 89:26 is a world-wide dominion, not merely dominion within the compass promised in the primeval times (Genesis 15:18; 2-Chronicles 9:26), in which case it ought to have been said ובנהר (of the Euphrates). Nor does the promise, however, sound so definite and boundless here as in Psalm 72:8, but it is indefinite and universal, without any need for our asking what rivers are intended by נהרות. נתן יד בּ, like שׁלח (in Isaiah 11:14, of a giving and taking possession. With אף־אני (with retreated tone, as in Psalm 119:63, Psalm 119:125) God tells with what He will answer David's filial love. Him who is the latest-born among the sons of Jesse, God makes the first-born (בּכור from בּכר, to be early, opp. לקשׁ, to be late, vid., Job 2:1-13 :21), and therefore the most favoured of the "sons of the Most High," Psalm 82:6. And as, according to Deuteronomy 28:1, Israel is to be high (עליון) above all nations of the earth, so David, Israel's king, in whom Israel's national glory realizes itself, is made as the high one (עליון) with respect to the kings, i.e., above the kings, of the earth. In the person of David his seed is included; and it is that position of honour which, after having been only prelusively realized in David and Solomon, must go on being fulfilled in his seed exactly as the promise runs. The covenant with David is, according to Psalm 89:29, one that shall stand for ever. David is therefore, as Psalm 89:30 affirms, eternal in his seed; God will make David's seed and throne לעד, into eternal, i.e., into such as will abide for ever, like the days of heaven, everlasting. This description of eternal duration is, as also in Sir. 45:15, Bar. 1:11, Taken from Deuteronomy 11:21; the whole of Psalm 89:30 is a poetic reproduction of 2-Samuel 7:16.