5 It was the Synagogue therefore, that is, they that there worshipped God after a godly sort, but yet for the sake of earthly things, for the sake of these present things (for there are ungodly men who seek the blessings of present things from demons: but this people was on this account better than the Gentiles, because although it were blessings present and temporal, yet they sought them from the One God, who is the Creator of all things both spiritual and corporal). When therefore those godly men after the flesh were observing— that is that Synagogue which was made up of good men, men for the time good, not spiritual men, such as were the Prophets therein, such as were the few that understood the kingdom heavenly, eternal— that Synagogue, I say, observed what things it received from God, and what things God promised to that people, abundance of things earthly, land, peace, earthly felicity: but in all these things were figures, and they not perceiving what was there concealed in things figured, thought that God gave this for a great matter, and had nothing better to give to men loving Him and serving Him: they remarked and saw certain sinners, ungodly, blasphemers, servants of demons, sons of the Devil, living in great naughtiness and pride, yet abounding in such things earthly, temporal, for which sort of things they were serving God themselves: and there sprang up a most evil thought in the heart, which made the feet to totter, and almost slip out of God's way. And behold this thought was in the people of the Old Testament: I would it be not in our carnal brethren, when now openly there is being proclaimed the felicity of the New Testament....
6. “How good is the God of Israel!” But to whom? “To men right in heart”. To men perverse what? Perverse He seems. So also in another Psalm He says: “With a holy man holy You shall be, and with the innocent man innocent You shall be, and with the perverse man perverse You shall be.” What is, perverse You shall be with the perverse man? Perverse the perverse man shall think You. Not that by any means God is made perverse. Far be it: what He is, He is. But in like manner as the sun appears mild to one having clear, sound, healthy, strong eyes, but against weak eyes does dart hard spears, so to say; the former looking at it it does invigorate, the latter it does torture, though not being itself changed, but the man being changed: so when you shall have begun to be perverse, and to you God shall seem to be perverse, you are changed, not He. That therefore to you will be punishment which to good men is joy. He calling to mind this thing, says, “How good is the God of Israel to men right in heart!”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)