Charles Ellicott Commentary John 5:16

"And for this cause the Jews persecuted Jesus, because he did these things on the sabbath." — John 5:16 (ASV)

The words, “and sought to slay Him,” should be omitted. They have been inserted in some manuscripts to explain the first clause of John 5:18. For “He had done,” read He was doing. The word is in the imperfect tense, expressing continuance or custom. It is either that from this one instance they generalise a law of practice to justify their persecution, or that some of the earlier unrecorded miracles were also performed on the Sabbath. (Compare Luke 6:1-11.)