Dies Domini pt 13 -
"
the Sabbath ...is therefore rooted in the depths of God's plan. This is why
unlike many other laws - it is not within the context of strictly cultic (Jewish) stipulations but within
the Decalogue the "ten words" which represent the very
pillars of moral life inscribed on the human heart!! In setting this commandment within the context of the basic structure of ethics, Israel and then the church declare that they consider it not just a matter of community religious discipline but a defining and indelible expression of our relationship to God, announced and expounded by biblical revelations.
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CCC -- Catholic Catechism
2056
The word "Decalogue" means literally "ten words."11 God revealed these "ten words" to his people on the holy mountain. They were written "with the finger of God,"
12 unlike the other commandments written by Moses.13 They are pre-eminently
the words of God. They are handed
on to us in the books of Exodus
14 and Deuteronomy.
15 Beginning with the Old Testament, the sacred books refer to the "ten words,"
16 but it is
in the New Covenant in Jesus Christ that
their full meaning will be revealed.
2072 Since they express man's fundamental duties towards God and towards his neighbor, the
Ten Commandments reveal, in their primordial content,
grave obligations.They are fundamentally immutable, and
they oblige always and everywhere. No one can dispense from them. the Ten Commandments are engraved by God in the human heart.
...
2175 Sunday is expressly distinguished from the sabbath which it follows chronologically every week;
for Christians its ceremonial observance replaces that of The Sabbath. In Christ's Passover,
Sunday fulfills the spiritual truth of the Jewish Sabbath and announces man's eternal rest in God. For worship under the Law prepared for the mystery of Christ, and what was done there prefigured some aspects of Christ:107
Those who lived according to the old order of things have come to a new hope,
no longer keeping The Sabbath, but the Lord's Day, in which our life is blessed by him and by his death.108
2176 The celebration of
Sunday observes the moral commandment inscribed by nature in the human heart to render to God an outward, visible, public, and regular worship "as a sign of his universal beneficence to all."109
Sunday worship fulfills the moral command of the Old Covenant, taking up its rhythm and spirit in the weekly celebration of the Creator and Redeemer of his people.
2190 The Sabbath, which represented the completion of the first creation, has been replaced by Sunday which recalls the new creation inaugurated by the Resurrection of Christ.