The glory of Lebanon shall come (comp. Isaiah 35:2; Isaiah 41:19). Considered as imagery, the representation is that the barren hills which stand about Jerusalem shall, in the new state of things, be decked with tall and beautiful forest trees, all the sylvan scenery of Lebanon being transported to Southern Palestine, so as to encompass the city of God with a garden as delightful as that of Eden.
The spiritual meaning is that graces of all kinds shall abound in and around the holy city, and shall make it beautiful and glorious. The fir tree, the pine tree, and the box together (comp. Isaiah 41:19, where the same words occur in the same order; and, for the trees intended, see the comment on that passage).
To beautify the place of my sanctuary. Not with "avenues of cedars and plane trees leading up to it" (Delitzsch), which was a style of ornamentation quite unknown to the lie-brews; but with groves, and thickets, and sylvan glades, and wooded slopes all around it, as round the Syrian temples in the Lebanon.
The place of my feet. The Jewish temple, as the special place of God's presence upon earth, was frequently termed "God's footstool" (1 Chronicles 28:2; Psalms 99:5; Psalms 132:7; Lamentations 2:1). He that towers above the heavens had there set his foot.
The metaphor is transferred to the renovated Zion.