Psalm 30:7

Lord, by thy favour thou hast made my mountain to stand
strong
The psalmist found himself mistaken, and acknowledges it; that as it was not owing to his own merit that he enjoyed the prosperity that he did, so neither was the continuance of it owing to his goodness, power, and strength, but to the free grace and favour of God; as the church of God is compared to a mountain, and the several individuals of believers are like to Mount Zion, so the soul of a child of God may be called his mountain, which is made strong by the Lord as to its state in Christ, being set on him, the Rock of ages, and sure foundation, where it is safe and secure; and as to its grace, whenever it is in any strong exercise, which is altogether owing to the favour of God, and continues as long as he pleases;

thou didst hide thy face, [and] I was troubled;
the Lord may hide his face from his people, and yet their state be safe; their mountain stands strong in that respect; yet this generally produces a change of frames; it gives trouble, and faith and hope become feeble and languid in their acts and exercises; this shows the changeableness of frames, that they are not to be depended upon; that they are entirely owing to the pleasure of God, and that rejoicing only should be in him: very likely some regard is had to the affair of Absalom's rebellion, which came unawares, unthought of, when David was in the greatest prosperity and security.