John Calvin Commentary Psalms 20:2

"Send thee help from the sanctuary, And strengthen thee out of Zion;" — Psalms 20:2 (ASV)

May he send you help. That is to say, may he help you from Mount Zion, where he commanded the ark of the covenant to be placed, and chose for himself a dwelling-place. The weakness of the flesh will not allow people to soar up to heaven, and therefore, God comes down to meet them, and by the external means of grace shows that he is near them.

Thus the ark of the covenant was to his ancient people a pledge of his presence, and the sanctuary an image of heaven. But as God, by appointing Mount Zion to be the place where the faithful should continually worship him, had joined the kingdom and priesthood together, David, in putting into the lips of the people a prayer for help from Zion, was undoubtedly mindful of this sacred bond of union.

Therefore I conjecture that this psalm was composed by David in his old age, and about the close of his life. Some think he spoke of Zion by the Spirit of prophecy before it had been appointed that the ark should be placed there; but this opinion seems strained, and to have little probability.