Short answer: Isaiah 40:29 promises that God supplies strength precisely to those who have none left: "He giveth power to the faint; and to them that have no might he increaseth strength" (KJV). The qualification for receiving God's strength in this verse is not capability — it is depletion.
The context: comfort for an exhausted people
Isaiah 40 opens a major turn in the book. The first thirty-nine chapters carry heavy warnings of judgment; chapter 40 begins, "Comfort ye, comfort ye my people, saith your God" (v. 1, KJV). It speaks to a people facing — or living in — exile, whose national life has collapsed.
The chapter builds an argument. It contrasts the frailty of human beings ("All flesh is grass," v. 6) with the permanence of God's word (v. 8). It piles up images of God's incomparable greatness: measuring waters in the hollow of His hand (v. 12), nations as a drop in a bucket (v. 15), naming every star and not missing one (v. 26).
Then comes the pastoral question in verse 27: why do you say, "My way is hid from the LORD"? Verses 28–31 are the answer. God does not faint or grow weary (v. 28) — and, verse 29 says, He gives that inexhaustible strength away.
What it means, phrase by phrase
"He giveth power to the faint." Giveth — not sells, not lends in exchange for performance. The recipient is the faint: someone whose energy has run out. Isaiah has already established in verse 28 that God Himself never faints; verse 29 draws the line from His inexhaustibility to our emptiness.
"And to them that have no might." The Hebrew is emphatic — those without strength, at zero. Not the somewhat tired. The depleted.
"He increaseth strength." The idea is multiplying or making abundant. God doesn't merely top up the tank; He enlarges the supply.
Verse 30 makes the point unmistakable by inverting expectation: "Even the youths shall faint and be weary, and the young men shall utterly fall" (KJV). Natural vigor runs out. Verse 31 then gives the famous conclusion: "But they that wait upon the LORD shall renew their strength; they shall mount up with wings as eagles; they shall run, and not be weary; and they shall walk, and not faint" (KJV).
Notice the order in verse 31 — mount up, run, walk. Some readers see a deliberate descent: the extraordinary moments, then sustained effort, then the plain daily plod that is often the hardest to keep. Others read it simply as a poetic sweep. Either way, the promise covers the ordinary as well as the dramatic.
Cross-references
- Isaiah 40:31 — they that wait upon the LORD shall renew their strength.
- 2 Corinthians 12:9–10 — "my strength is made perfect in weakness" (KJV).
- Philippians 4:13 — I can do all things through Christ who strengthens me.
- Matthew 11:28–30 — come unto me, all ye that labour and are heavy laden.
- Psalm 73:26 — my flesh and my heart fail, but God is the strength of my heart.
- Ephesians 3:16 — strengthened with might by His Spirit in the inner man.
How to apply it today
The first application is to stop disqualifying yourself. Many believers wait until they feel spiritually together before coming to God, which is exactly backward here. The verse names the faint and the strengthless as the recipients. Emptiness is the address this promise is delivered to.
Second, note what verse 31 attaches the renewal to: waiting on the LORD. That is the same active, expectant trust described in Psalm 27:14 — prayer, attention to God's word, refusing to look elsewhere for the supply. Renewal in Isaiah 40 is not automatic; it's connected to where you turn.
Third, be careful about what this verse promises. It is not a guarantee that you will feel energetic, or that God will remove the demands on you. Elijah, immediately after his greatest victory, collapsed under a juniper tree and asked to die — and God's first response was food and sleep (1 Kings 19:4–7). Scripture treats physical rest as part of how God cares for exhausted people, not a failure of faith. If you are burned out, this verse and a genuine day off are not in competition.
Faithful Christians differ over how much of "renewed strength" is felt versus simply given — some testify to a real inner lift, others to a bare capacity to keep going with no feeling attached. Isaiah's promise is about sufficiency for the road, not about sensation.
Frequently Asked Questions
Does Isaiah 40:29 promise physical energy? The passage speaks broadly of strength and endurance rather than specifying physical stamina alone. Its setting — a nation drained by exile — suggests strength for the whole person: to keep going, keep hoping, keep walking. Scripture elsewhere treats physical rest as God's ordinary provision (1 Kings 19:5–7), so this verse doesn't replace sleep and care.
What does "wait upon the LORD" mean in verse 31? It's confident, expectant reliance on God rather than passivity — the same idea as Psalm 27:14. It involves prayer, trust in His promises, and refusing to source your strength elsewhere. The renewal is tied to that turning toward God.
Why does the verse say youths will faint? It's a deliberate contrast. If even those with the most natural vigor run out, then no amount of human capacity is enough, and everyone finally needs the strength only God gives. The point isn't that young people are weak — it's that all human strength has a floor.
Can I claim this verse when I'm burned out? Yes — it's addressed precisely to those with no might left. At the same time, Scripture doesn't set God's strengthening against ordinary means like rest, food, medical help, and community. Elijah received all of those from God's hand before receiving God's word.