Hast thou an arm like God? - The arm is the symbol of strength. The question here is, whether Job would venture to compare his strength with the omnipotence of God?
Or canst thou thunder with a voice like him? - Thunder is a symbol of the majesty of the Most High, and is often spoken of as the voice of God; see Psalms 29:1-11. The question here is, whether Job could presume to compare himself with the Almighty, whose voice was the thunder?