Mark’s short Gospel appears to be a narrative of Our Lord’s public years; but the incidents in his narrative are not there simply as events in his life. No, Mark chose today's incident to convey to us a basic truths about Christianity. Jesus defended the right of the disciples to harvest handfuls of grain on the Sabbath, but the words he used have a wide application beyond the events of that Sabbath Day.
Jesus said, “The Sabbath was made for man, not man for the Sabbath. That is why the Son of Man is lord even of the Sabbath.”
Take the second part of that first. As “lord of the Sabbath” Jesus had the authority to allow his Church to move the Lord’s Day from Saturday to Sunday.
Taking the first part. In saying that the Sabbath was made for man, not man for the Sabbath Jesus wass agreeing with Exodus 23: 12 which states, “For six days you may do your work, but on the seventh day you must rest, that your ox and your ass my also have rest and the son of your maidservant and the alien may be refreshed.”In saying that the law of the Sabbath was made for our good Jesus was saying something of a wider application. He was saying that all religious rules were formed to make mankind happy. They need not be applied if they have a deadly effect on people.