John Calvin Commentary Psalms 106:3

"Blessed are they that keep justice, And he that doeth righteousness at all times." — Psalms 106:3 (ASV)

Blessed are they that keep judgment. I make a distinction between this and the preceding verse, yet in such a way as to preserve the connection between them. For the prophet, having declared the magnitude of God’s power to be such that no tongue could utter all its praises, now says that praises of the lip alone are not acceptable to God, but that the concurrence of the heart is indispensable; indeed, that even our entire conduct must be in harmony with this practice.

Now, when he first commands to keep judgment, and then to work righteousness, he gives us a short description of genuine godliness. I have no doubt that in the former clause he describes the sincere affection of the heart, and in the latter, he refers to external works. For we know there is nothing but the mere shadow of righteousness, unless a man sincerely devotes himself to the practice of honesty.

He requires perseverance, too, so that no one may imagine that he has discharged this duty properly, except for the one whose constant and continued aim is to live righteously and justly. We see many who have only an empty profession; others show some signs of virtue but do not maintain a consistent course of conduct.