Rashi on Deuteronomy 32:4/רש"י על דברים ל״ב:ד׳

1הצור תמים פעלו THE ROCK, HIS WORK IS PERFECT — Although He is strong (הצור!) yet when He brings punishment upon those who transgress His will, He does not bring it in a flood of anger, but in deliberate judgment, because תמים פעלו HIS WORK IS PERFECT.

2אל אמונה A GOD OF FAITHFULNESS — faithful to recompense the righteous their righteousness in the world to come; and even though He defers their recompense, in the end He will prove faithful (אמן) to His promise.

3ואין עול AND WITHOUT INJUSTICE — even to the wicked He pays the reward for their meritorious deeds, but in this world (Sifrei Devarim 307:11; cf. Rashi on Deuteronomy 7:10).

4צדיק וישר הוא — The meaning is: All acknowledge His judgment to be just (צדיק), and this is befitting and right of them (ישר), i.e., He is declared צדיק by the mouth of men, וישר, and it is right for them to declare Him צדיק, as righteous.