Who said, "Skin for skin! A man will give up all he owns in exchange for his life"?

Answer: Satan

Satan said this to the LORD (Job 2:4-5), claiming Job would curse God to His face if his own flesh and bones were struck.

““Skin for skin!” Satan replied. “A man will give up all he owns in exchange for his life. But stretch out Your hand and strike his flesh and bones, and he will surely curse You to Your face.””— Job 2:4-5 (BSB)