Albert Barnes Commentary Job 40:9

"Or hast thou an arm like God? And canst thou thunder with a voice like him?" — Job 40:9 (ASV)

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 . The question here is whether Job could presume to compare himself with the Almighty, whose voice was the thunder.