At his footstool; before the ark, which is so called, 1 Chronicles 28:2 Psalms 132:7. For he is holy; or rather, for it, to wit, the ark, is holy; it is consecrated to be a pledge of God's presence, and the only place of God's public worship.
Related Commentaries of Psalms 99:5
Psalms 99:5
5 Exalt ye the LORD our God, and worship at his footstool; for he is holy.