Chapter 23;v3

שֵׁשֶׁת יָמִים תֵּֽעָשֶׂה מְלָאכָה וּבַיּוֹם הַשְּׁבִיעִי שַׁבַּת שַׁבָּתוֹן מִקְרָא־קֹדֶשׁ כָּל־מְלָאכָה לֹא תַֽעֲשׂוּ שַׁבָּת הִוא לַֽיהֹוָה בְּכֹל מֽוֹשְׁבֹֽתֵיכֶֽם

Six days shall work be done; but the seventh day is the sabbath of rest, a holy gathering; you shall do no work in it; it is the sabbath of the Lord in all your dwellings.

This weekly portion discusses the holidays. Why does it interrupt with a statement about the six days of the week and the Sabbath?

The Gaon of Vilna explains that the “six days” may be construed to mean not the six days of the week but the six Festivals of the Jewish year on which, according to the Law, work connected with the preparation of food is permitted; namely, the first and last days of Passover, Shavuot, Rosh HaShanah, and the first and last days of Sukkot (according to Biblical law, only one day each).

Accordingly, Verse 3: “Six days shall work be done…” fits into the portion as a general statement concerning the holidays, which are treated in greater detail in the verses that follow. “Six days shall work be done”: there are six holidays on which all work connected with the preparation of food may be done, “but on the Seventh Day is a Sabbath of Sabbaths” – the seventh holiday is Yom Kippur, the Day of Atonement, the ‘Sabbath of Sabbaths’ on which work connected with the preparation of food is forbidden.(Vilna Gaon)