The Lord Jesus Christ opposed Israel’s religious rulers over legalistic practices that they thought commended them to God and kept them in power. These rulers had condemned His disciples for picking and eating grain on the Sabbath. Near the end of this confrontation, He said:

…If you had known what this means, ‘I desire mercy, and not sacrifice,’ you would not have condemned the guiltless. Matthew 12:7 English Standard Version (ESV)

And in a separate report of the event:

…He said to them, “The Sabbath was made for man, not man for the Sabbath. So the Son of Man is lord even of the Sabbath.” Mark 2:27-28 (ESV)

The Gospels go on to describe how the Lord healed a man on the Sabbath. Rather than repent and believe in God, Israel’s rulers viewed these presumed violations as a pretext to kill the Savior.

The Reformation leader, John Calvin, had insight into the texts:

But if you knew …Christ conveys an indirect reproof to the [religious rulers] for not considering why ceremonies were appointed, and to what object they are directed. …God declares…that he sets a higher value on mercy than on sacrifice, employing the word mercy…for [services] of kindness [and] sacrifices [as] the outward service of the Law…

…Though piety is justly reckoned to be as much superior to charity as God is higher than men, yet believers, by practicing justice towards each other, prove that their service [for] God is sincere. It is not without reason that this subject is brought [to] the notice of hypocrites, who imitate piety by outward signs, and yet pervert it by confining their laborious efforts to the carnal worship alone…

Those trying to trap and kill the Lord and thereby save themselves and their power missed His offer of mercy. They missed that:

The Sabbath was made for man. …Those persons judge amiss who turn [the Sabbath into] man’s destruction…which God appointed for his benefit. …Is not this a foolish attempt to overturn the purpose of God, when they demand to the injury of men that observation of the Sabbath which he intended to be advantageous?

But they are mistaken, I think, who suppose that in this passage the Sabbath is entirely abolished; for Christ simply informs us what is the proper use of it. Though he asserted, a little before, that he is Lord of the Sabbath, yet the full time for its abolition was not yet come, because the veil of the temple was not yet rent, (Matthew 27:51.)

Calvin then analyses the sanction with which Christ acted:

For the Son of man is Lord even of the Sabbath. …He declares that he has received authority to exempt his followers from the necessity of observing the Sabbath. The Son of man, (he says,) in the exercise of his authority, can relax the Sabbath in the same manner as other legal ceremonies. And certainly out of Christ the bondage of the Law is wretched, from which he alone delivers those on whom he bestows the free Spirit of adoption, (Romans 8:15.)

The rulers meant to sacrifice the Lord of Sabbath in order to keep their lives; Christ meant mercy in giving up His.

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Lest we be carried away with the thought that Calvin advocated doing away with Sabbath observance, Calvin sums up his understanding of the Sabbath from the scriptures in his Institutes of the Christian Religion:

…First, that during our whole lives we may aim at a constant rest from our own works, in order that the Lord may work in us by his Spirit; secondly that every individual, as he has opportunity, may diligently exercise himself in private, in pious meditation on the works of God, and, at the same time, that all may observe the legitimate order appointed by the Church, for the hearing of the word, the administration of the sacraments, and public prayer: And, thirdly, that we may avoid oppressing those who are subject to us.

And contemporary theologian R. C. Sproul continues the debate on the topic of Sabbath keeping as do others here, here, here, and here. In any case, we would do well to strictly adhere to that severe admonition:

Whatever you do, in word or deed, do everything in the name of the Lord Jesus, giving thanks to God the Father through him. Colossians 3:17 (ESV)

Jesus As Lord of the Sabbath – A sermon from Dr. R.C. Sproul

And

Jesus Is Lord of the Sabbath – A sermon from Dr. R.C. Sproul