Isaiah 40 28-31
28 Hast thou not known, hast thou not heard, that the everlasting God, the Lord, the creator of the ends of the earth, fainteth not, neither is weary?
29 He giveth power to the faint; and to them that have no might he increaseth strength.
30 Even the youths shall faint and be weary, and the young men shall utterly fall;
31 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.