en_tn/jhn/09/16.md

he does not keep the Sabbath

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's signs prove he is not a sinner. Alternate translation: "A sinner can not do such signs!" (See: rc://en/ta/man/jit/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.