40:31 wait upon the LORD. The Hebrew word for “wait upon” does not mean “serve,” but rather “wait for” or “look for.” It was used by Jacob in Genesis 49:18, when he cried out, “I have waited for thy salvation, O LORD.” It appears prophetically on the lips of the dying Savior, when He said: “I waited patiently for the LORD” (Psalm 40:1).
40:31 renew their strength. Literally, “renew” means “exchange.” Those who look to the infinite, omniscient, omnipotent Creator for their supply of order, intelligence and power shall exchange their weakness and foolishness for His strength and wisdom. This is a marvelous energy conversion process!