Remember the day, Shabbat, to set it apart for God. You have six days to labor and do all your work, but the seventh day is a Shabbat for Adonai your God. On it, you are not to do any kind of work — not you, your son or your daughter, not your male or female slave, not your livestock, and not the foreigner staying with you inside the gates to your property. For in six days, Adonai made heaven and earth, the sea and everything in them; but on the seventh day he rested. This is why Adonai blessed the day, Shabbat, and separated it for himself. ~ Exodus 20:8-11, CJB
There are many believers who condemn other believers for not worshipping God on the Sabbath, which to them is Saturday and never Sunday. Now while these Sabbath keepers are correct in saying that God established the Sabbath as a day of rest and a day of worship, they are wrong in pronouncing judgment against other believers who do not rest and worship on the Sabbath (Saturday), and they are wrong for accusing the same believers of sinning against God, just because they are not following God’s Old Testament pattern of work and rest. For sure, the Divine Truth is that, even though the Old Testament’s Mosaic Law Sabbath is a weekly mandated day of rest and worship, which usually is observed on a Saturday, in the new covenant ANY day of the week that a person receives the Lord and enters into the rest He offers is a Sabbath rest!
Put differently, Christ Jesus is every believer’s Sabbath rest. Remember, He says: “Come to me, all of you who are struggling and burdened, and I will give you rest” ~ Matthew 11:28, CJB. In this verse, the “rest” that the Lord gives is the same “rest” Father God takes after He completed the work of Creation. Father God rests not because He was tired but because He was finished—His work was done. Thus, His rest was a spiritual rest (an eternal rest), because on the day His rest begins there was no mention of an evening and morning.
Then too, because Christ Jesus’ work on this Earth has ended, He also is resting, eternally. He is resting because He has fulfilled (completed) ALL of the demands of the Law (satisfied all of the Law’s requirements), which called for perfect obedience and unwavering faithfulness. Now, if the Lord has fulfilled the Law, then that means He also has fulfilled the commandment about keeping the Sabbath holy. Therefore, since Father God made the Sabbath for mankind, and not the other way around (cf. Mark 2:27), which means Father God intended for the Sabbath to benefit human beings and not enslave them, this is the reason why the Sabbath rest is not about keeping a special day (Saturday or Sunday), but rather the keeping of the Sabbath rest is about ending/ceasing all of mankind’s righteous, holy, and good-life efforts, and finding in their place Christ Jesus’ spiritual/eternal rest that consists of a peaceful conscience, a relieved mind, and/or a calm soul.
The Lord’s perfect fulfillment of the Law (via His life, death, burial, and resurrection) means that in Christ Jesus believers are now able to keep ALL of the Law faithfully and obediently. More important, since Christ Jesus is believers’ Sabbath rest, they now can cease from their own efforts (stop following their righteousness by works system of worship) and instead depend on and trust in the righteous work of Someone else (depend on Christ Jesus’ finished work).
The writer of Hebrews concurs, saying:
So there remains a Shabbat-keeping for God’s people. For the one who has entered God’s rest has also rested from his own works, as God did from his. ~ Hebrews 4:9-10, CJB
In other words, because the Lord is believers’ Sabbath rest, then entering into the rest of the Lord is the only kind of Sabbath “works” Father God expects believers in Christ Jesus to do so that they will be sure to keep the Sabbath holy. For these reasons, apostle Paul says:
So don’t let anyone pass judgment on you in connection with eating and drinking, or in regard to a Jewish festival or Rosh-Hodesh or Shabbat. These are a shadow of things that are coming, but the body is of the Messiah. ~ Colossians 2:16-17, CJB
The bottom line is that under the Law, the Old Testament’s Sabbath rest was only a shadow of the Original who was to replace it, and this Original is Christ Jesus (cf. Hebrews 10:1). As a shadow of the Sabbath rest that is in Christ Jesus, the Old Testament’s Sabbath rest, which the Mosaic Law established as a weekly mandated Sabbath day, was a Sabbath rest that, no matter how faithfully and religiously it was kept, never could have brought mankind back into right standing with Father God. For this reason, the real (the Original) Sabbath rest of God only can be understood and experienced by those Christ Jesus believers who not only have had their sins forgiven but also have been redeemed by the Lamb of God’s shed blood and atoning sacrifice.