"15. The man departed, and told the Jews that it was Jesus, which had made him whole. 16. And therefore did the Jews persecute Jesus, and sought to slay him, because he had done these things on the sabbath day. 17. But Jesus answered them, My Father works hitherto, and I work. 18. 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. " (St. John 5:15-18)
The Gospel of St. John connects the two concepts of Sonship and Godhood together as Christ explains that He works on the Sabbath as His Father does. St. John Chrysostom and St. Thomas Aquinas note that the explanation of Christ, that His Father and He work, is valid because He has equal authority with God. The Angelic Doctor continues that if He is equal to God then He is God by nature.
St. John Chrysostom:
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“Were He not the Son by nature, and of the same substance, this defense would be worse than the former accusation made. For no prefect could clear Himself from a transgression of the king’s law, by urging that the king broke it also. But, on the supposition of the Son’s equality to the Father, the defense is valid. It then follows, that as the Father worked on the Sabbath without doing wrong: the Son could do so likewise.”*
St. Thomas Aquinas:
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“Again, he said that as the Father works, so he works. This answers the accusation of the Jews about his breaking the Sabbath: for this would not be a valid excuse unless he had equal authority with God in working. It was for this reason they said he made himself equal to God.”
“For the Evangelist says that the Jews persecuted Christ because he broke the Sabbath, because he said God is his Father, and because he made himself equal to God. But Christ is either a liar or equal to God. But if he is equal to God, Christ is God by nature.”* [2]