For who is God besides Jehovah? David here, deriding the foolish inventions of men, who, according to their own fancy, make for themselves tutelary gods,. confirms what I have said before, that he never undertook any thing but by the authority and command of God. If he had passed beyond the limits of his calling, he could not with such confidence have said that God was on his side. Besides, although in these words he opposes to the true God all the false gods invented by men, his purpose, at the same time, is to overthrow all the vain hopes in which the world is wrapped up, and by which it is carried about, and prevented from resting in God. The question which David here treats of is not the bare title and name of God, but he declares that whatever assistance we need we should seek it from God, and from no other quarter, because he alone is endued with power: Who is strong except our God? We should, however, attend to the design of David, which I have first adverted to, namely, that, by confidently representing God as opposed to all his enemies, and as the leader, under whose standard he had valiantly fought against them, he means to affirm that he had attempted nothing according to his own fancy, or with an evil and condemning conscience.

For who is God save the Lord? - Who is God except Yahweh? The idea is, that no other being has evinced the power, the wisdom, and the goodness which properly belong to the true God; or, that the things which are implied in the true nature of God are found in no other being.
Or who is a rock save our God? - See Psalm 18:2. There is no one who can furnish such safety or defense; no one under whose protection we can be secure in danger. Compare Deuteronomy 32:31.

For who is God save the Lord? - "For who is Eloah, except Jehovah?" None is worthy of adoration but the self-existent, eternal, infinitely perfect, and all-merciful Being.
Or who is a rock - A fountain emitting continual supplies of grace and goodness.

For who is God save the Lord?.... Or Jehovah: there is but one God, and Jehovah is he; there is none besides him, nor any like him: there are many that are called gods, nominal deities, who are not by nature gods; fictitious ones, the idols of the Gentiles, made of gold, silver, brass, wood, and stone; but there is but one true God: there are gods, in an improper sense, as civil magistrates; but there is none really and truly so but the Lord; which is to be understood, not of Jehovah the Father, to the exclusion of the Son and Spirit; for the Son is Jehovah, and the Spirit is Jehovah; both are so called, as well as the Father, and all three one God;
or who is a rock save our God? to have recourse to for shelter and protection; or to trust to, and build upon, for eternal life and salvation. False gods are rocks; but not like ours, our enemies themselves being judges, Deuteronomy 32:31; so Apollo at Delphos is called the Delphian rock (n): the words seem to be taken from, or at least there is in them a reference to, 1-Samuel 2:2.
(n) , Sophoclis Oedipus, v. 472.

(Hebrews.: 18:32-35) The grateful description of the tokens of favour he has experienced takes a new flight, and is continued in the second half of the Psalm in a more varied and less artificial mixture of the strophes. What is said in Psalm 18:31 of the way and word of Jahve and of Jahve Himself, is confirmed in Psalm 18:32 by the fact that He alone is אלוהּ, a divine being to be reverenced, and He alone is צוּר, a rock, i.e., a ground of confidence that cannot be shaken. What is said in Psalm 18:31 consequently can be said only of Him. מבּלעדי and זוּלתי alternate; the former (with a negative intensive מן) signifies "without reference to" and then absolutely "without" or besides, and the latter (with ı̂ as a connecting vowel, which elsewhere has also the function of a suffix), from זוּלת (זוּלה), "exception." The verses immediately following are attached descriptively to אלהינוּ, our God (i.e., the God of Israel), the God, who girded me with strength; and accordingly (fut. consec.) made my way תמים, "perfect," i.e., absolutely smooth, free from stumblings and errors, leading straight forward to a divine goal. The idea is no other than that in Psalm 18:31, cf. Job 22:3, except that the freedom from error here is intended to be understood in accordance with its reference to the way of a man, of a king, and of a warrior; cf. moreover, the other text. The verb שׁוּה signifies, like Arab. swwâ, to make equal (aequare), to arrange, to set right; the dependent passage Habakkuk 3:19 has, instead of this verb, the more uncoloured שׁים. The hind, איּלה or איּלת, is the perfection of swiftness (cf. ἔλαφος and ἐλαφρός) and also of gracefulness among animals. "Like the hinds" is equivalent to like hinds' feet; the Hebrew style leaves it to the reader to infer the appropriate point of comparison from the figure. It is not swiftness in flight (De Wette), but in attack and pursuit that is meant, - the latter being a prominent characteristic of warriors, according to 2-Samuel 1:23; 2-Samuel 2:18; 1-Chronicles 12:8. David does not call the high places of the enemy, which he has made his own by conquest "my high places," but those heights of the Holy Land which belong to him as king of Israel: upon these Jahve preserves him a firm position, so that from them he may rule the land far and wide, and hold them victoriously (cf. passages like Deuteronomy 32:13; Isaiah 58:14). The verb למּד, which has a double accusative in other instances, is here combined with ל of the subject taught, as the aim of the teaching. The verb נחת (to press down = to bend a bow) precedes the subject "my arms" in the singular; this inequality is admissible even when the subject stands first (e.g., Genesis 49:22; Joel 1:20; Zac 6:14). קשׁת נחוּשׁה a bow of brazen = of brass, as in Job 20:24. It is also the manner of heroes in Homer and in the Ram-jana to press down and bend with their hand a brazen bow, one end of which rests on the ground.

Who - Our Lord is the only God, and therefore there is none, that can hinder him from accomplishing his own work.