Commentary on Bamidbar 21:10

‎הֲמִן־הַסֶּ֣לַע הַזֶּ֔ה נוֹצִ֥יא לָכֶ֖ם מָֽיִם

“Can we draw water for you from this rock?” (Bamidbar 21:10) 

The Arvei Nahal taught that the source of existence for everything is its name. The word “סלע” — rock, when spelled in the middle letters of its Millui (spelling of the letters) — סמ״ך למ“ד עי“ן — contains the word “מים” (water).

This alludes that Moshe Rabbeinu drew water for the nation from within the rock itself.