*Minor differences ignored. Grouped by changes, with first version listed as example.
The LORD liveth; (u) and blessed [be] my rock; and exalted be the God of the rock of my salvation.
(u) Let him show his power that he is the governor of all the world.
The Lord liveth; and blessed be my rock; and exalted be the God of the rock of my salvation. See Gill on Psalm 18:46.
47 Jehovah liveth, and blessed is my rock,
And the God of my refuge of salvation is exalted.
48 The God who giveth me vengeance,
And bringeth nations under me;
49 Who leadeth me out from mine enemies,
And exalteth me above mine adversaries,
Delivereth me from the man of violence.
The formula חי־יהוה does not mean "let Jehovah live," for the word יחי would be used for that (vid., 2-Samuel 16:16; 1-Samuel 10:24), but is a declaration: "the Lord is living." The declaration itself is to be taken as praise of God, for "praising God is simply ascribing to Him the glorious perfections which belong to him; we have only to give Him what is His own" (Hengstenberg). The following clauses also contain simply declarations; this is evident from the word ירוּם, since the optative ירם would be used to denote a wish. The Lord is living or alive when He manifests His life in acts of omnipotence. In the last clause, the expression צוּר (rock) is intensified into ישׁעי צוּר אלהי (the God of my refuge, or rock, of salvation), i.e., the God who is my saving rock (cf. 2-Samuel 22:3). In the predicates of God in 2-Samuel 22:48, 2-Samuel 22:49, the saving acts depicted by David in vv. 5-20 and 29-46 are summed up briefly. Instead of מוריד, "He causes to go down under me," i.e., He subjects to me, we find in the psalm ויּדבּר, "He drives nations under me," and מפלטי instead of מוציאי; and lastly, instead of חמס אישׁ in the psalm, we have here חמסים אישׁ, as in Psalm 140:2. Therefore the praise of the Lord shall be sounded among all nations.
*More commentary available at chapter level.