Isaiah 40:31
31 But those who wait for Yahweh will renew their strength. They will mount up with wings like eagles. They will run, and not be weary. They will walk, and not faint.
World English Bible (WEB)
On Isaiah 40:31: the context of this famous verse about renewing strength while waiting, the image of "eagles' wings" and why it is read in weariness and waiting.
Isaiah 40:31 stands at the head of the verses about not losing strength while waiting. It is the close of a long chapter that speaks openly of tiredness and exhaustion; so it does not ignore weariness but answers it.
The verse pictures hope not as passive stillness but as renewed strength: running without growing weary, walking without fainting. The image of "eagles' wings" makes this renewal a picture that stays in the mind.
You can move to the chapter below to read the wider context that promises strength to the weary. Related collections on hope and waiting bridge to other verses on the same theme.