“The sabbath was made for man, not man for the sabbath. That is why the Son of Man is lord even of the sabbath.”-- Mark 2:27-28
This is often taken, correctly, as a rebuke to arid legalism. But why should the sabbath's being made for man imply that the Son of Man is Lord of the sabbath?
Quoting the Biblical Second Letter of St. Peter, and works of St. Irenaeus and St. Athanasius, the Church instructs us that:
The Word became flesh to make us "partakers of the divine nature":-- Catechism of the Catholic Church, 460.
"For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God."
"For the Son of God became man so that we might become God."
"The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods."
Jesus is not merely a son of man, i.e., a human being, He is the Son of Man--the Messiah, the definitive human being who brings the human super-organism up into zoe, into the supernatural bliss of the inner life of the Trinity.
Following St. Augustine, in his De Trinitate, we may imagine the inner life of the Trinity as follows: The Father is pure Being. This Being knows Himself, and that eternally generated Self-Knowledge is the Son, Whom we call the Logos, the Word. He may be approximately imagined as the Son of the Father the way your thoughts are the child of your mind. Perfect Being, in Perfect Self-Knowledge, is filled with Delight at the Contemplation of His Own Perfection. This Delight, this Joy, this Love, is the Holy Spirit. If, after having done the right thing, you contemplate yourself with pleasure, and this thought fills you with happiness, then you have an approximate experience of the way the Holy Spirit is eternally re-inspired in the life of the Trinity. Be cautioned, however, that this analogy, like all human attempts to wrestle with the riddle of the Divine nature, is misleading in many ways. E.g., although the inner life of the Trinity is One because, among many other reasons, it is like the life of a single human mind, it is also Threefold in a way we cannot imagine: the Being, the Knowledge, and the Love are Three distinct Persons in a way that our brains' matter, our thoughts, and our emotions are very much not.
To be taken up into the Beatitude, (i.e., the blessedness, the bliss) of the Trinity, we must become like God. The Beatitudes themselves, Christ's often-difficult-to-follow advice about how to become "blessed," are part of how God means to transform us into beings capable of enjoying everlasting life with Him, strong enough to look straight at the sun of His Glory. In our present sinfulness, such strong Light might prove a hellish fire rather than a radiance to be cherished: this is the traditional Eastern Orthodox doctrine of Hell: we all attain to God's presence upon death, but only some of us are transformed enough into saintliness to truly delight in it.
God is eternally contemplating with pure Self-knowledge and Pure self-love, the Perfection of His Own Being. Although He doesn't need anything from us to complete His perfect beatitude, He created us and invites us into His Love merely because He overflows with infinite Love. Since God does not need our love for Him, the sabbath does Him no good. He is already perfect: nothing we do can benefit Him.
However, in the metaphorical account of the beginning of the world in Genesis, we read that on the seventh day, God rested, and contemplated the goodness of His creation. Resting from our labors on the sabbath to contemplate the goodness of God, to cherish the goodness of our families, to reflect that all the good things in our lives come ultimately not from our own efforts but as free gifts from Him, makes us more like God, Who finds endless bliss in contemplating His own Perfection and His own good creation of our cosmos. Unlike some pagan deity of Greece or Mesopotamia, God had no need to create us to worship Him on the sabbath. He doesn't feast on the smoke of our sacrifices like a hungry ghost, or like the gods in the works of Homer. So he did not make us for the sabbath. Instead, He decreed the sabbath in His Law given to the Jews as part of the project He fulfilled in the Son of Man, Whose teachings, Whose Crucifixion, Whose Resurrection, bring us into the everlasting bliss of sharing in the contemplation of the Perfection of God. The door to a more blissful life--now, and forever--is open every Sunday at every parish. God made it just for you. Why not walk through it?