Until I went into the sanctuary of God - The word "sanctuary" we now apply to a place of public worship; and, thus understood, the passage here would mean that he learned the truth on the subject only by the statements and disclosures made there in regard to the divine plans and dealings, and the results of human conduct. This interpretation makes good sense, and is in itself true, but it is not the idea in the original. The word "sanctuary" in the Old Testament, in the singular number, is applied to the tabernacle, or the temple, or, more especially to the most holy place in the tabernacle or the temple; the place of the unique dwelling of God. Thus understood the idea would be that he learned the solution of the mystery "there." But these were not places of instruction, and it cannot be supposed that the reference is to either of them. The word in the original is in the plural number - sanctuaries - things that God regarded as holy; and the meaning seems to be, that the only solution of the case was to be learned from those things which pertained to God's most holy and secret places; or in those places which were nearest to him, and where he most clearly manifested himself. The difficulty was not to be solved by any mere human reasoning - by the powers of man, away from God; it was to be learned in the presence of God himself, and in the disclosures which He made about his divine plans and purposes. The psalmist had tried his own powers of reason, and the subject was above his reach. The only solution of the difficulty was to be obtained by a near approach to God himself. There the mystery could be solved, and there it was solved. The "end" of all this, as disclosed by God, would determine why, it was permitted, and would remove the perplexity of the mind.
Then understood I their end - literally, their after things; that is, the things which will occur to them hereafter. That solves all the difficulty. There will be a judgment hereafter, and dark as things may now appear, it will be seen in the end, or in the result, that exact and equal justice will be done to all.

Until I went into the sanctuary - Until, in the use of thy ordinances, I entered into a deep consideration of thy secret counsels, and considered the future state of the righteous and the wicked; that the unequal distribution of temporal good and evil argued a future judgment; that the present is a state of trial; and that God exercises his followers according to his godly wisdom and tender mercy. Then light sprang up in my mind, and I was assured that all these exercises were for our benefit, and that the prosperity of the wicked here was a prelude to their destruction. And this I saw to be their end.
That this Psalm was written during the captivity, there is little room to doubt. How then can the psalmist speak of the sanctuary? There was none at Babylon; and at Jerusalem it had been long since destroyed? There is no way to solve this difficulty but by considering that מקדשי mikdeshey may be taken in the sense of holy places - places set apart for prayer and meditation. And that the captives had such places in them captivity, there can be no doubt; and the place that is set apart to meet God in, for prayer, supplication, confession of sin, and meditation, is holy unto the Lord; and is, therefore, his sanctuary, whether a house or the open field. Calmet thinks by holy meditations a view of the Divine secrets, to which he refers, Psalm 73:24, is here meant.

Until I went into the (h) sanctuary of God; [then] understood I their end.
(h) Until I entered into your school and learned by your word and Holy Spirit that you order all things most wisely and justly.

Until I went into the sanctuary of God,.... The tabernacle or house of God, where the Word of God was read and explained, prayer was made, and sacrifices offered up, and where fellowship was had with the saints, and communion with God himself; which for one hour or moment is preferable to all the prosperity of the wicked, during their whole life. This shows that though the psalmist was beset with the temptation, yet not overcome; it did not so far prevail as to cause him to neglect public worship, and relinquish the house of God, and the ordinances of it; and it is right, under temptations, doubts, and difficulties, to attend the public ministrations, which is the way and means to have relief under temptations, to have doubts resolved, and difficulties removed: some by "the sanctuary of God" understand the Scriptures, which are holy and of God, and are profitable for instruction, and are to be consulted and entered into by a serious reading of and deep meditation on them; whereby may be known the happiness that is prepared for the saints in the other world, and the misery of the wicked, and hereby judgment may be made of the present case and condition of each: others interpret it of the world of spirits, which may be entered into by contemplation; when it may be observed that the spirits of just men upon their dissolution possess unspeakable joys and glories, and the souls of the wicked are in inconceivable torments:
then understood I their end; both of the godly and of the wicked; that the end of the righteous is peace, rest, salvation, and eternal life, and the end of the wicked is ruin, destruction, and death; see Psalm 37:35.

went into the sanctuary--to enquire (compare Exodus 25:22; Psalm 5:7; Psalm 27:4).

Until - 'Till I consulted the word of God. He alludes to the practice of those times, which was, in difficult cases to resort to God's sanctuary, and the oracle therein. Their end - There I learned that their prosperity was short.