For thou hast been my hope Here we may suppose, either that he calls to his remembrance such benefits as he had formerly received, or that he congratulates himself upon deliverance which he had presently experienced. There is much probability in either supposition. Nothing animates our hopes more than the recollection of the past goodness of God, and, in the midst of his prayers, we frequently find David indulging in reflections of this kind. On the other hand, the remainder of the psalm is occupied with returning praise to God for his present goodness; and there is no reason why we should not suppose, that these words before us form the commencement of the thanksgiving. In that case, the Hebrew particle, which we have rendered for or because, may be understood rather in an affirmative sense, surely or certainly. In the verse which follows, he expresses the confidence which he had that he would dwell from this time forth in the sanctuary of the Lord. I cannot altogether agree with those who think that David was still in his state of exile from his native country when this was written, and is merely to be understood as promising to himself the certainty of his return. He would seem rather to be rejoicing in restoration already obtained, than assuaging his grief by anticipation of it in the future; and this will be still more apparent, when we come to consider the immediate context. It is noticeable, that now when he was returned from his banishment, and established within his own palace, his heart was set more upon the worship of God than all the wealth, splendor, and pleasures of royalty. We have his testimony in other parts of his writings, that in the worst calamities which he endured, he experienced nothing which could be compared to the bitterness of being shut out from the ordinances of religion; and now he accounts it a higher pleasure to lie as a suppliant before the altar, than to sit upon the throne of a king. By the words which immediately follow, he shows that he did not, like too many uninformed persons, attach a superstitious importance to the mere externals of religion, adding, that he found his safety under the shadow of God's wings. Ignorant persons might conceive of God as necessarily confined to the outward tabernacle, but David only improved this symbol of the Divine presence as a means of elevating the spiritual exercises of his faith. I would not deny that there may be an allusion to the cherubim when he speaks of the shadow of God's wings. Only we must remember, that David did not rest in carnal ordinances, the elements of the world, but rose by them and above them to the spiritual worship of God.

For thou hast been a shelter for me - A place of refuge; a place where I have found safety. He refers here to what had occurred in former times. God had protected him when in danger, and he pleads that fact as a reason why God should now interpose and deliver him. That reason seems to be founded on two considerations:
(a) God had thus shown that he had power to deliver him; and
(b) it might be expected that God who is unchangeable, and who had interposed, would manifest the same traits of character still, and would not leave him now.
Both of these are proper grounds for prayer.
And strong tower from the enemy - See the notes at Psalm 18:2.

Those hast been a shelter for me - During the whole duration of the captivity God marvellously dealt with the poor Jews; so that, although they were cast down, they were not utterly forsaken.

For thou hast been a shelter for me,.... Or "refuge" (y), from avenging justice; a hiding place and covert from the storms and tempests of divine wrath; a shadow and a screen from the heat of Satan's fiery darts, and the blast of his terrible temptations, Isaiah 25:4;
and a strong tower from the enemy: from Satan the devouring lion, from furious persecutors, and every other enemy; see Proverbs 18:10; and this experience the psalmist had of protection from the Rock in former times made him desirous of being led to it now.
(y) "asylum", Tigurine version, Vatablus; "perfagium", Cocceius; "refugium", Michaelis.

shelter . . . and strong tower--repeat the same sentiment.