Jesus broke the law of resting on the Sabbath by preaching, doing work. The Jewish law stated that you aren't to do any work on the Sabbath at all, just rest. However, he didn't sin for working on the Sabbath, because he was preaching God's word, but he did sin by breaking the law. Of course, I guess it wasn't a sin because it was a stupid law that God didn't like (if he did, why would Jesus have broken it?), but you understand what I mean, right?