The observance of the 7th day Sabbath was specifically given to Israel. After the New Covenant was established by Christ, the Sabbath days were deemed to be "shadows" of the reality of Christ, who is Lord of the Sabbath, and who said that the Sabbath was made for man, not man for the Sabbath.
Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days: which are a shadow of things to come; but the body is of Christ. (Col 2:16,17)
Not what the fourth Commandment says at all...
Exo 20:8 "Remember the Sabbath day, to keep it holy.
Exo 20:9 Six days you shall labor and do all your work,
Exo 20:10 but the seventh day is the Sabbath of the LORD your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who is within your gates.
Exo 20:11
For in six days the LORD made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the LORD blessed the Sabbath day and hallowed it.
Notice when the Sabbath was given, The seventh day of creation. Jacob, whose name was changed to Israel, was still about 2000years in the future
Gen 26:5 because Abraham obeyed My voice and kept My charge, My commandments, My statutes, and My laws."
Here we find Abraham keeping God's Commandments before Isaac, Israel's father, is born.
What about the NT?
Paul kept the Sabbath and taught on it...
Act 13:44 On the next Sabbath almost the whole city came together to hear the word of God.
Act 17:1 Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where there was a synagogue of the Jews.
Act 17:2 Then Paul,
as his custom was, went in to them, and for three Sabbaths reasoned with them from the Scriptures,
same custom as Christ...
Luk_4:16 So He came to Nazareth, where He had been brought up. And as His custom was, He went into the synagogue on the Sabbath day, and stood up to read.
Paul taught the gentiles on the Sabbath...
Act_13:42 So when the Jews went out of the synagogue, the Gentiles begged that these words might be preached to them the next Sabbath.
Why didn't Paul just say come on back tomorrow, the first day of the week?
Now is there NT instruction to keep the Sabbath?
Heb 4:4 For He has spoken in a certain place of the seventh day in this way: "AND GOD RESTED ON THE SEVENTH DAY FROM ALL HIS WORKS";
Heb 4:9 There remains therefore a rest for the people of God.
The word for rest here is...
G4520
σαββατισμός
sabbatismos
sab-bat-is-mos'
From a derivative of G4521; a “sabbatism”, that is, (figuratively) the repose of Christianity (as a type of heaven): - rest.
Derived from G4521
G4521
σάββατον
sabbaton
sab'-bat-on
Of Hebrew origin [H7676]; the Sabbath (that is, Shabbath), or day of weekly repose from secular avocations (also the observance or institution itself); by extension a se'nnight, that is, the interval between two Sabbaths; likewise the plural in all the above applications: - sabbath (day), week.
Funny how the one Commandment God told us to remember is the one everyone wants to forget.
Oh and if this command was given to Israel, then think about this...
Gal_6:16 And as many as walk according to this rule, peace and mercy be upon them, and upon the Israel of God.
And who did God make the New Covenant with?
Heb_8:8 Because finding fault with them, He says: "BEHOLD, THE DAYS ARE COMING, SAYS THE LORD, WHEN I WILL MAKE A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH—
Finding fault with them,
Psa 95:10 For forty years I was grieved with that generation, And said, 'It is a people who go astray in their hearts, And they do not know My ways.'
Psa 95:11 So I swore in My wrath, 'They shall not enter My rest.' "
The problem was not the Law, it was their hard, unconverted heart.