Jamieson, Fausset and Brown on John 2:18-22

18-22. What sign showest thou unto us, seeing that thou doest these things?--Though the act and the words of Christ, taken together, were sign enough, they were unconvinced: yet they were awed, and though at His very next appearance at Jerusalem they "sought to kill Him" for speaking of "His Father" just as He did now (Joh 5:18), they, at this early stage, only ask a sign.