There are two points in this verse. “Cast thy burden upon the Lord.” Whatever the trial or difficulty may be, cast it upon the Lord. It is not that the trial goes always—here (in this Psalm) it would not till judgment came; but “He shall sustain thee.” It is better than the trials going. It is the direct coming in of God to ourselves, to our own souls, the sense of His interest in us, His favor, His nearness, that He comes in to help us in our need. It is a divine condition of the soul, which is better than absence of evil. God is a sure help to sustain us.
The second point is the infallible faithfulness of God. He shall never suffer the righteous to be moved. Tried they may be, but He cannot suffer evil in the world to prevail, nor will He. We may learn to trust by the evil, but in trusting we know the Lord will keep, and the extreme character of the evil only shows the rather that God must come in―makes His intervention necessary.
J.N.D.