Matthew Henry Commentary Psalms 99:6-9

"Moses and Aaron among his priests, And Samuel among them that call upon his name; They called upon Jehovah, and he answered them. He spake unto them in the pillar of cloud: They kept his testimonies, And the statute that he gave them. Thou answeredst them, O Jehovah our God: Thou wast a God that forgavest them, Though thou tookest vengeance of their doings. Exalt ye Jehovah our God, And worship at his holy hill; For Jehovah our God is holy." — Psalms 99:6-9 (ASV)

The happiness of Israel is demonstrated by referring to the most effective governors of that people. They made God's word and law their rule in everything, knowing that they could not otherwise expect that their prayers should be answered. They all wonderfully prevailed with God in prayer; miracles were performed at their request. They pleaded for the people, and obtained answers of peace.

Our Prophet and High Priest, of infinitely greater dignity than Moses, Aaron, or Samuel, has received and declared to us the will of the Father. Let us not only exalt the Lord with our lips, but give him the throne in our heart; and while we worship him upon his mercy-seat, let us never forget that he is holy.