‘Oh that the salvation of Israel were come out of Zion!
When YHWH restores the fortunes (or ‘brings back the captivity) of his people,
Then will Jacob rejoice,
Israel will be glad.'
The psalmist finishes on a note of longing. O that Israel's deliverance had come. This confirms that they are here seen as under some kind of misfortune. In Job 42:10 the verb ‘restores the fortunes' clearly signifies a restoral of fortunes to Job. He is only a captive to his misery. And this fits all the other places where the verb is used. Thus it is possibly the best translation here. It could therefore refer to a period of subjection under the Philistines, or some other enemy of Israel..
But even if we translate as being in ‘captivity', it would not necessarily mean exile. It could equally signify being in subjection in the land. So we are probably to see them as being under the iron rule of some foreign monarch, subject to tribute and in a period when they were being treated badly. ‘From Zion' probably has in mind Mount Zion from which, speaking in an earthly way, God will act. Or the thought may be that the psalmist was looking to Zion's king, the anointed of YHWH, to bring about the deliverance. Either way the deliverance will be of God. And that is the final certainty, that YHWH will restore His people. And then they will be glad and rejoice.
‘Brings back the captivity', or ‘restores the fortunes', of His people.' See for the use of the phrase Job 42:10; Hosea 6:11; Amos 9:14; Ezekiel 16:53; Zephaniah 2:7.
So the message of the Psalm is of God's calling to the account the folly of the nations, both as regards Himself, and especially as revealed in their attitude towards His people, having very much in mind here His true people. The thought is that His being and nature are so obvious in the light of creation and conscience, and His people so precious, that humanly speaking, from the psalmist's point of view, God could only question the behaviour of the world in its treatment of His people.