Read John 5:18 Using Other Translations
Therefore the Jews sought the more to kill him, because he not only had broken the sabbath, but said also that God was his Father, making himself equal with God.
This was why the Jews were seeking all the more to kill him, because not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God.
So the Jewish leaders tried all the harder to find a way to kill him. For he not only broke the Sabbath, he called God his Father, thereby making himself equal with God.