Isaiah 40: 29-31

(RSV) Revised Standard Version

29: He gives power to the faint, and to those who have no might He increases strength. 

30: Even the youths shall faint and be weary, and the young men shall utterly fall

31: but those who 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.