Vol 26.31 - Vayakhel 1 Spanish French Audio Video
"And you, though I have charged you to command them concerning the work of the mishkon, let it not be an easy matter for you to set the Shabbos aside on account of that work.
You must still preserve My Shabbos: Though you may be preoccupied in the rush of the work of the mishkan, nevertheless Shabbos should not be set aside on account of it. This is indicated by the fact that every time the word "Ach" or "Rak" appear they convey the idea of limiting or excluding. Here "Ach" appears so as to exclude Shabbos from any work of the mishkan.