Do you not know?
Have you not heard?
The Lord is the everlasting God, the Creator of the ends of the earth
He will not grow tired or weary
and His understanding no one can fathom

He gives strength to the weary
and increases the power of the weak
Even youths grows tired and weary
and young men stumble and fall

But those who hope in the Lord will renew their strength
They will soar on wings like eagles
They will run and now grow weary
They will walk and not be faint

(Isaiah 40:28-31 NIV)