39 Or “the Jewish authorities”; Grk “the Jews.” In NT usage the term Ἰουδαῖοι (Ioudaioi) may refer to the entire Jewish people, the residents of Jerusalem and surrounding territory, the authorities in Jerusalem, or merely those who were hostile to Jesus. Here the author refers to the authorities or leaders in Jerusalem. (For further information see R. G. Bratcher, “ ‘The Jews’ in the Gospel of John,” 26 [1975]: 401–9.)
40 Grk “answered and said to him.”
41 The request “What sign can you show us” by Jesus’ adversaries was a request for a defense of his actions—a mark of divine authentication. Whether this was a request for a miracle is not entirely clear. Jesus never obliged such a request. Yet, ironically, the only sign the Jewish leadership will get is that predicted by Jesus in 2:19—his crucifixion and resurrection. Cf. the “sign of Jonah” in the synoptics (Matt 12:39, 40; Luke 11:29–32).

In other versions

So the Jews said to him, “What sign do you show us for doing these things?”

The Jews then responded to him, “What sign can you show us to prove your authority to do all this?”

So the Jews replied to him, “What sign will you show us for doing these things?”

But the Jewish leaders demanded, “What are you doing? If God gave you authority to do this, show us a miraculous sign to prove it.”

So the Jews answered and said to him, “What sign do you show to us, because you are doing these things?”

Then answered the Jews and said unto him, What sign shewest thou unto us, seeing that thou doest these things?

Public Domain