The purpose of the Ten Commandments are to tell us what it means to be obedient. They cannot save us.
Chrisy didn’t nullify the Ten Commandments. The heart of the Pharisees were such that they were trying to figure out how close to the line could they get, without going over, and still be considered keeping the commandments.
Christ redefined the keeping of the Commandments from being one of action to being one of intent.