Wait on the Lord - This is the sum of all the instruction in the psalm; the main lesson which the psalm is designed to convey. The object is to induce others, from the experience of the psalmist, to trust in the Lord; to rely upon Him; to come to Him in trouble and danger; to wait for His interposition when all other resources fail. Compare Psalms 25:3.
Be of good courage - The Hebrew word here means, “be strong.” That is, do not faint. Do not be dismayed. Still hope and trust in the Lord.
He shall strengthen thine heart - He will strengthen “thee.” He will enable you to perform your duties, and to triumph over your enemies. See the notes at Isaiah 40:31.
Wait, I say, on the Lord - Repeating an idea with which the heart was full; a lesson resulting from his own rich experience. He dwells upon it as a lesson which he would fix deeply in the mind, that in all times of danger and difficulty, instead of despondency, instead of sinking down in despair, instead of giving up all effort, we should go forward in the discharge of duty, putting our trust solely in the Lord.