Jesus announced his return to the one who sent him, the Father in heaven (17:1–7). But the Pharisees misunderstood him. They thought he was leaving Judea to visit the Gentiles (non-Jewish people). These were people whom Pharisees would never visit.
After Jesus returned to the Father, the Jewish leaders would no longer be able to find him.
and where I am, you cannot come: These Pharisees, still in spiritual darkness, could not enter heaven. So Jesus would be beyond their reach there.