John Calvin Commentary Psalms 140:12

"I know that Jehovah will maintain the cause of the afflicted, And justice for the needy." — Psalms 140:12 (ASV)

I have known; that God, etc. There can be no question that David here seals or corroborates his prayer by turning his thoughts and discourse to the providential judgments of God, for, as I have already said, doubtful prayer is no prayer at all. He declares it to be a thing known and ascertained that God will surely deliver the afflicted.

As God may permit for a time, however, and allow good and upright persons to be severely tried, David suggests a consideration that may counter this temptation: that God does so deliberately, so that He may relieve those who are in affliction and rescue those who are oppressed. He accordingly says in express words that He will be the judge of the poor and the afflicted.

In this way, David encourages both others and himself under continued troubles, until the proper time for deliverance arrives. He intimates that though he might be universally considered an object of pity—being exposed to the fury of the wicked and not being immediately delivered by God's hand—he would not give way to despair, but would remember that it was precisely God's role to undertake the cause of the poor. It would weaken the passage if we considered David to be speaking merely of his own individual case.

He infers (Psalms 140:13) that the righteous would give thanks to God and be safe under His help. For the particle אך, ach, which is often adversative in the Hebrew, is here affirmative and denotes inference or consequence from what was previously stated. Though the godly may be silenced for a time, and through the force of trouble may not raise the praises of God, David expresses his conviction that what was taken away would be swiftly restored, and they would celebrate the loving-kindness of the Lord with joy and eagerness.

Since this is not easily believed in times of trial, the affirmation previously mentioned is inserted. We must endeavor, though with a struggle, to rise to a confident persuasion that however low they may be brought, the Lord’s people will be restored to prosperity and will soon sing His praises.

The second clause of the verse gives the reason for their thanksgiving. He speaks of this as being the ground of the praises of the righteous: that they experience God’s care for them and concern for their salvation. For to dwell before God’s face is to be cherished and sustained by His fatherly regards.