And in my prosperity I said— There should not be a full stop at the end of the 6th verse, but after the words stand strong in the 7th; where the next period should begin, Thou didst hide thy face; I was troubled. The word שׁלו shalev rendered prosperity, denotes peace and tranquillity, arising from an affluent prosperous condition. When God had settled him quietly on the throne, he thought that all his troubles were over, and that he should enjoy uninterrupted happiness; that God had made his mountain so strong that it should never be moved: i.e. had placed him secure from all danger, as though he had taken refuge in an inaccessible mountain; or made his prosperity firm, and no more subject to alteration than a mountain is liable to be removed out of its place; or raised him to an eminent degree of honour and prosperity; a mountain by its height being a very natural representation of a superior condition, remarkable for power, affluence, and dignity. He had taken the fortress of Mount Sion, which was properly his mountain, as he had fixed upon it for his dwelling: it was strong by nature, and rendered almost impregnable by the fortifications that he had added to it. This he regarded as the effect of God's favour to him, and promised himself that his peace and happiness for the future should be as undisturbed and unshaken as Mount Sion itself. To hide one's face, is to refuse to see, or be seen, by another, and argues displeasure, and a denial of assistance and favour. The Psalmist means, that when God withdrew his protection, displeased with his presumption and the security that he had fondly promised himself, he was immediately disturbed by fresh troubles, and his dream of uninterrupted tranquillity vanished. He refers, I believe, to the two invasions of the Philistines, soon after they found that he had been anointed king over Israel.
2 Samuel 5:17; 2 Samuel 5:25. In this unexpected distress, he cried unto the Lord, and in his supplication said as in Psalms 30:9-10. Chandler.