Exodus 31:13

ואתה דבר אל בני ישראל SPEAK THOU ALSO UNTO THE CHILDREN OF ISRAEL — AND thou, although I have given thee charge to command them concerning the work of the Tabernacle let it not appear a light thing to thee to set the Sabbath aside on account of that work. אך את שבתתי תשמרו BUT NEVERTHELESS MY SABBATHS SHALL YE KEEP — Even though you be anxious and alert to do the work promptly the Sabbath nevertheless you must not set aside on its account. The words אך and רק wherever they occur in Scripture have limitative force (Rosh Hashanah 17b; cf. Rashi on Rosh Hashanah 17b on אכין ורקין). Here Scripture intends by the word אך to except the Sabbath from the days on which the work of the Tabernacle may be done. כי אות היא ביני וביניכם FOR IT IS A SIGN BETWEEN ME AND YOU — There is a mark of distinction in the relation that exists between us, viz., the fact that I have chosen you by letting you inherit for rest that day on which “I” rested. לדעת TO KNOW — (not, “for you to know”, but) for the nations of the world to know through it, כי אני ה' מקדשכם THAT I AM THE LORD THAT DOTH SANCTIFY YOU.

וְאַתָּ֞ה דַּבֵּ֨ר אֶל־בְּנֵ֤י יִשְׂרָאֵל֙ לֵאמֹ֔ר אַ֥ךְ אֶת־שַׁבְּתֹתַ֖י תִּשְׁמֹ֑רוּ כִּי֩ א֨וֹת הִ֜וא בֵּינִ֤י וּבֵֽינֵיכֶם֙ לְדֹרֹ֣תֵיכֶ֔ם לָדַ֕עַת כִּ֛י אֲנִ֥י יְהֹוָ֖ה מְקַדִּשְׁכֶֽם׃

Speak also to the children of Yisra᾽el saying, Verily my sabbaths shall you keep: for it is a sign between me and you throughout your generations; that you may know that I am the Lord who sanctifies you.