Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
This psalm is ascribed to David, and there is no reason to doubt the correctness of the title in this respect. The psalm is not an original composition, but is made up, with slight alterations, of parts of two other psalms, Psa 57:7-11; Psa 60:5-12.
When the psalm was so arranged, or why the parts of two former psalms were thus brought together to form a new composition, it is impossible now to determine. It "may" have been for a mere purpose of art; or it may, more probably, have occurred when the two parts of psalms already in use might be so combined as to be adapted to some new event. It may have been, also, that what had been expressed "on two different occasions" might now be fulfilled or accomplished "on some one occasion," and that thoughts which had been expressed separately before might now be unitedly uttered in praise. Rosenmuller supposes that the psalm in its present form was arranged on the return from the captivity at Babylon, and that the parts of the two separate psalms were found to be suitable for a national song at that time, and were therefore thus brought together. This supposition would have much probability if the psalm were not ascribed to David; and perhaps this fact need not be an insuperable objection - since, if the two psalms from which this is compiled were the work of David, the author of the arrangement might without impropriety attribute the composition itself to David.
There are some slight variations in the psalm, as here arranged, from the original psalms; but why these were made cannot now be determined. Substantially all that will be necessary in the exposition of the psalm will be to notice these variations.
O God, my heart is fixed - Prepared, suited, ready. See the notes at Psa 57:7. In Psa 57:7, this is repeated: "My heart is fixed; O God, my heart is fixed:" indicating that there "might" have been some doubt or vacillation caused by the circumstances then existing, and the repetition would have respect to that, as if the psalmist had been unsettled and wavering for a time, but was at last firm. In such circumstances it would not be unnatural to "repeat" the assertion, as if there were no longer any doubt. In the beginning of a psalm, however, where there had been no previous expression or feeling of doubt so far as appears, there would be no propriety in repeating the assertion.
I will sing and give praise - See the notes at Psa 57:7.
Even with my glory - This is not in Psa 57:1-11. It is literally here, "truly my glory." In Psa 57:8, however, the expression, "Awake up, my glory," occurs, and this seems to correspond with that language. It means here that it was his glory - his honor - thus to be employed in giving praise to God. It was worthy of all that there was elevated in his nature; of all that constituted his glory; of his highest powers. At no time is man employed in a more noble and lofty work than praise.
Awake, psaltery and harp ... - This is copied without change from Psa 57:8.
I will praise thee, O Lord ... - This is taken from Psa 57:9. The only change is the substitution here of the name יהוה Yahweh for אדני 'Adonāy. Why that change was made is unknown.
For thy mercy ... - This is taken from Psa 57:10. The only change is in the expression "above the heavens," instead of "unto the heavens." The sense is essentially the same. The particular idea here, if it differs at all from the expression in Psa 57:1-11, is, that the mercy of God seems to "descend" from heaven upon man, or "comes down" from on high.
Be thou exalted ... - This is taken from Psa 57:11. The only change in the Hebrew is in the insertion of the word "and," "and thy glory above all the earth."
That thy beloved may be delivered - The word rendered "beloved," and the verb rendered "may be delivered," are both in the plural number, showing that it is not an individual that is referred to, but that the people of God are intended. This is taken without any alteration from Psa 60:5. In that psalm the prayer for deliverance is grounded on the afflictions of the people, and the fact that God had given them "a banner that it might be displayed because of the truth," - or, in the cause of truth. See the notes at that psalm. In the psalm before us, while the prayer for deliverance is the same, the reason for that prayer is different. It is that God is exalted; that his mercy is above the heavens; that his glory is above all the earth, and that he is thus exalted that he may interpose and save his people.
Save with thy right hand, and answer me - The Hebrew here is the same as in Psa 60:5, where it is rendered "and hear me."
God hath spoken ... - This is taken, without change, from Psa 60:6. See the notes at that place.
Gilead is mine ... - This is taken from Psa 60:7. The only change is the omission of the word and before "Manasseh."
Moab ... - This is fallen from Psa 60:8. The only change is in the close of the verse. Instead of "Plilistia, triumph thou because of me" Psa 60:8, it is here, "Over Philistia will I triumph." Why the change was made is unknown.
Who will bring me ... - This is taken, without alteration, from Psa 60:9.
Wilt not thou, O God ... - This is taken from Psa 60:10, with no change in the Hebrew, except that the word "thou" (in the first member of the verse) is omitted.
Give us help from trouble ... - This is copied from Psa 60:11.
Through God we shall do ... - This also is taken from Psa 60:12, without change.
Thus the psalm, though made up of parts of two separate psalms, is complete and continuous in itself. There is no break or discrepancy in the current of thought, but the unity is as perfect as though it had been an original composition. It is to be remarked, also, that though in the original psalms the parts which are used here have a different connection, and are separately complete there, yet as employed here, they seem to be exactly suited to the new use which is made of the language; and though the original "reasons" for the use of the language do not appear here, yet there is a sufficient reason for that language apparent in the psalm as rearranged. To an Israelite, also, there might be a new interest in the use of the language in the fact that words with which he was familiar, as employed for other purposes, "could" be thus combined, and made applicable to a new occasion in the national history.