Chabad.org — English translation + Rashi
Torah Temimah (Shabbos 31b): “על פי ה׳ יחנו” informs the definition of constructive vs. destructive acts on Shabbos.
English: Ulla said: he holds like Rabbi Yehudah, and Rabbi Yose holds that one who demolishes in order to build in its place — that is demolishing. … There it is different, since it is written “at the word of the Lord they encamp,” it is like one who demolishes in order to build in its place.
Halakhic analogy from the cloud’s movements — the constant dismantling and re-erection of the camp under Divine command informs the definition of constructive vs. destructive acts on Shabbos.
The Torah’s description of living under the cloud becomes a source for precise categories in the laws of Shabbos construction.