Psalms 99:8

8.O Jehovah our God The prophet here reminds them that God had heard their prayers because his grace and their piety harmonized. Consequently, encouraged by their exemplary success in prayer, their posterity ought to call upon God, not merely pronouncing his name with their lips, but keeping his covenant with all their heart. He farther reminds us that if God does not display his glory so bountifully, and so profusely in every age, the fault is with men themselves, whose posterity have either utterly forsaken, or greatly declined from the faith of the fathers. It is not to be wondered at that God should withdraw his hand, or at least not stretch it forth in any remarkable way, when he beholds piety waxing cold on the earth.

O God, thou hast been propitious to them. (123) From these words it is quite obvious that what the Psalmist had formerly said concerning Moses, Aaron, and Samuel, refers to the whole people; for surely they did not officiate as priests merely for their own benefit, but for the common benefit of all the Israelites. Hence the transition is more natural which he makes from these three to the remaining body of the people. For I neither restrict the relative, to these three persons, nor do I interpret them exclusively of the same, but I rather think that the state of the whole Church is pointed out; namely, that while God, at the prayers of the priests, was propitious to the Jews, he, at the same time, sharply punished them for their sins. For on the one hand, the prophet magnifies the grace of God in that he had treated the people so kindly, and had so mercifully forgiven their iniquity; on the other hand, he specifies those awful examples of punishment by which he punished them for their ingratitude, that their descendants might learn to submit themselves dutifully to him. For it must not be forgotten, that by how much God deals graciously with us, by so much will he the less easily endure that we should treat his liberality with scorn.