At that the Jews were all the more determined to kill him: not only was he breaking the Sabbath, he was also calling God his own Father, making himself equal to God.
In context
16And for this the Jews began to persecute Jesus: he did such things on the Sabbath. 17But he answered them, “My Father is at work to this very moment, and I am at work as well.” 18At that the Jews were all the more determined to kill him: not only was he breaking the Sabbath, he was also calling God his own Father, making himself equal to God. 19So Jesus answered them, “Very truly I tell you, the Son can do nothing on his own, only what he sees the Father doing. Whatever the Father does, the Son does the same. 20For the Father loves the Son and shows him everything he himself is doing; and he will show him greater works than these, so that you will be amazed.
