In verse 18 there is a break from the main story line as John provides background information about the Jews' disbelief. (See: [[rc://en/ta/man/translate/writing-background]])
This means Jesus does not obey the law about doing no work on the Jewish Day of Rest.
# How can a man who is a sinner do such signs?
This remark appears in the form of a question to emphasize that Jesus' signs prove he is not a sinner. AT: "A sinner can not do such signs!" (See: [[rc://en/ta/man/translate/figs-rquestion]])
# signs
This is another word for miracles. "Signs" give evidence that God is the all-powerful one who has complete authority over the universe.