The Son of Man is Lord even of the Sabbath.
Mark 2:28 (NIV)
When He healed people on the Sabbath, Jesus showed the true spirit of the holy day. He kept the Sabbath according to the ancient Hebrew scriptures—the Old Testament.
By claiming that He was the “Lord of the Sabbath” Jesus challenged the authority of the Jewish priests and rabbis. This challenge eventually led to His infamous trial and death on the cross.
It's important to notice that the Sabbath controversy in Jesus' day was not about which day of the week to observe as a day of rest and worship. That issue never came up. The questions that Jesus addressed were NOT about WHEN to keep the Sabbath, but HOW to keep it.