Why did the Jews want to kill Jesus?

John 19:7 NWT

The Jews answered him: “We have a law, and according to the law he ought to die, because he made himself God’s son.”

John 5:14-18 NWT

After this Jesus found him in the temple and said to him: “See, you have become well. Do not sin anymore, so that something worse does not happen to you.” The man went away and told the Jews that it was Jesus who had made him well. For this reason the Jews were persecuting Jesus, because he was doing these things during the Sabbath. But he answered them: “My Father has kept working until now, and I keep working.” This is why the Jews began seeking all the more to kill him, because not only was he breaking the Sabbath but he was also calling God his own Father, making himself equal to God.

Why did the Jews think Jesus was making himself equal to God by calling God "his own Father"?