Saying that the Sabbath is made for man is not the same as saying that the Sabbath was given to all of mankind. And the Torah makes it clear that 1. it was given to Israel and 2. its observance is a sign of the exodus.
It was a sign for worship....the Creator... In the commandment itself... Remember the Sabbath day, to keep it holy. Six days you shall labor and do all your work, but
the seventh day is the Sabbath of the LORD your God (Name). 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.
For in six days the LORD (Title: Creator) made (authority) the heavens and the earth, the sea, and all that is in them (Jurisdiction), and rested the seventh day. Therefore the LORD blessed the Sabbath day and hallowed it (Exodus 20: 8-11 NKJV).
These three components comprise what is known as a seal, and lend authority to the law. The Ten Commandments gain their validity only from the royal seal of the Creator God embodied in the Sabbath commandment. Without a royal seal, no law would be valid. Moreover, even with a royal seal, a law is only valid in the area of the king’s jurisdiction.
As our Lord... He promises ...
Isaiah 56:3-8 3 Let not the foreigner who has joined himself to the Lord say,
“The Lord will surely separate me from his people”; and let not the eunuch say,
“Behold, I am a dry tree.” 4 For thus says the Lord: “To the eunuchs
who keep my Sabbaths, who choose the things that please me and hold fast my covenant, 5 I will give in my house and within my walls a monument and a name better than sons and daughters; I will give them an everlasting name that shall not be cut off.
6
the foreigners who join themselves to the Lord, to minister to him, to love the name of the Lord, and to be his servants,
everyone who keeps the Sabbath and does not profane it, and holds fast my covenant — 7 my holy mountain, and make them joyful in my house of prayer; their burnt offerings and their sacrifices will be accepted on my altar;
for my house shall be called a house of prayer for all peoples.” 8 The Lord God,
who gathers the outcasts of Israel, declares, “I will gather yet others to him
besides those already gathered.”
Gen 2:3 And God blessed the seventh day, and sanctified it: because that in it He had rested from all his work which God created and made.
Ex 20:8 Remember the Sabbath Day to keep it holy.
There were, in fact, a full seven days of creation. On the seventh day He made the Sabbath. The Sabbath was and is made by rest not by work. We are to follow his example and rest from our "work". Sabbath is the day God commanded for us to set-apart. His children are obedient to His command. The Sabbath is also how we know we are worshiping the God of Creation, because He created for six days and rested on Shabbat (the seventh day). In Judaism, we are counted as sons when we do what the father does.