The impotent man that was healed seemed to oppose the authority of God (by virtue of which he believed himself healed) to the authority of man, which made it unlawful for him on the sabbath day to take up his bed and walk. The Jews, taking no notice of Christ's being God, or so much as a prophet sent from God, do not ask, Who was he? But, What man is that which said, & c.? opposing the command of God to the command of man. It is as much as if they had said; The law of God hath commanded that no burdens should be carried on the sabbath day; now, what is that man that dare teach thee or any one to do what is contrary to the law of God?
Related Commentaries of John 5:12
John 5:12
12 Then asked they him, What man is that which said unto thee, Take up thy bed, and walk?