Charles Spurgeon Commentary Isaiah 40:30-31

"Even the youths shall faint and be weary, and the young men shall utterly fall: but they that wait for Jehovah shall renew their strength; they shall mount up with wings as eagles; they shall run, and not be weary; they shall walk, and not faint." — Isaiah 40:30-31 (ASV)

Shall utterly fall: but they that wait upon the LORD shall renew their strength; they shall mount up with wings as eagles;

That is their first mode of progression, in which, perhaps, there is more flight than is good for them: They shall mount up with wings as eagles;–