אבן עזרא — אך את שבתתי תשמרו כי אות הִוא ביני וביניכם לדרתיכם לדעת

Q — Why is the mitzvah of Shabbat appended HERE, at the end of the mishkan instructions? And what does "לדעת כי אני ה' מקדשכם" add to mere abstention from melacha?

A — Ibn Ezra reads the placement as functional — even those engaged in the holiest work (mishkan construction) need to be reminded that Shabbat doesn't yield to "מלאכת הקודש." But the deeper move is his reading of "לדעת": Shabbat demands not only abstention but active KNOWLEDGE — and knowledge requires study. "וזה רמז שחייב אדם בכל שבת ללמוד דברי התורה." Two proofs: (1) the Shunamit's husband, surprised at her sudden trip to Elisha — "לא חדש ולא שבת" — implies that on Shabbat people regularly went to neviim and chachamim for Torah; (2) shmittah is the year-equivalent of Shabbat, and the Torah's prescribed activity for shmittah (Hakhel: "למען ישמעו ולמען ילמדו") establishes Torah study as the parallel weekly avodah for Shabbat. Shabbat is not merely a day of rest but a fixed weekly date with Torah.