The letter of the law that the Pharisees tried to keep was not enough—especially for us. We have to exceed the letter of the law. Here, Jesus was so specific about the continuance of the law from the Old Covenant to the New that He referred to the smallest punctuation and pronunciation marks contained in the written law, the "jot and tittle."
Most modern theology discards the letter in favor of the spirit, but one extreme is as bad as the other. The true Christian needs both the written letter of the law as well as its spirit to keep it properly.
To keep God's law properly, we have to learn to recognize the spirit of the law. The spirit of the law means God's original intent or purpose behind each law.
When God designed the Sabbath, for example, He intended it to be a blessing to human beings. He designed it to be a refreshing rest and an opportunity both to recuperate physically after six days of work and to draw close to Him in love and to worship Him, as well as to deepen love for the brethren through fellowship and outgoing concern.
Jesus knew the spirit of the Sabbath commandment. Therefore, He knew that the split second of divine effort involved in healing was a valid use of time on the Sabbath (Matthew 12:10-12). Because of Jesus' insight into the divine purpose behind the Sabbath, He freed the crippled worshipper of his burden. He experienced a wonderful and exciting blessing because Jesus understood the spirit of the law. God's law is always a blessing to those who recognize the spirit of the law.