Kommentar zu Schemot 31:17

וינפש AND WAS REFRESHED — Take it as the Targum renders it: ונח “and He rested”. Every form of נפש is derived from the noun נֶפֶש, soul; the idea is, that one calms his soul and takes breath when one reposes after the toil of labour. — And He of Whom it is written, (Isaiah 40:28) “[… the Lord, the Creator of the ends of the earth] fainteth not nor is He weary”, and Whose every action is accomplished by His mere command had the term “repose” written of (ascribed to) Himself in order to make comprehensible to the human ear what it can understand.

וביום השביעי שבת, seeing that on that day the creative activity of G’d had been completed, completion spells rest,

ביני ובין בני ישראל אות היא לעולם, “between Me and the Children of Israel it is an everlasting symbol.” It is possible to understand that the word לעולם in this verse means that the Sabbath is a symbol attesting to the fact that G’d created the world out of nothing. This is why our verse describes how the Sabbath functions as a sign (proof) for the entire world. Cessation of creative activity signals that the person so refraining believes that G’d made the world in six days (without drawing on existing raw materials).
The words ביני ובין בני ישראל, “between Me and between the Children of Israel,” teaches that there was a hidden aspect which had been conveyed to the Israelites privately. There is a mystical, hidden aspect to the Sabbath.” When a king issues a command to a son or trusted servant, something not everyone knows about, he is apt to say to his son: “remember the thing that is between me and you.” These are the things which had been agreed upon between father and son without any written protocol having been made of them. This is the reason our sages explained in Beitzah 16 in the name of Rabbi Shimon bar Yochai that G’d gave the Israelites all the commandments in public with the exception of the Sabbath. He based himself on the words in our verse [the word לעולם, derived from נעלם, “hidden, secret,” is probably the way Rabbi Shimon understood our verse. Ed.]. Seeing that the Sabbath is one of the Ten Commandments and as such was certainly given to the Jewish people in public at Mount Sinai, what did the Rabbi mean when he spoke of the Sabbath having been given secretly, in private? Moreover, Isaiah 48,16 states specifically that “from the beginning I did not speak to you in secret, etc.” How do we reconcile his words with those of Rabbi Shimon bar Yochai? Also, in Psalms 138,4 David exclaims: “All the kings of the earth shall praise You, O Lord, for they have heard the words You spoke.” What did Rabbi Shimon have in mind? The sages referred to a hidden, mystical element which is part of the entire complex of the Sabbath laws and concept, not to the actual positive and negative commandments which have all been spelled out in public.”