“Language is the house of being,” applies to the Toltec Book of Wisdom or the Four Agreements by Don Miguel Ruiz: We create with our word. We create our reality. We can also harm ourselves and others through the misuse of the word. As it says in John 1:1—”In the beginning was the Word. And the Word was with God. And the Word was God.”
“Language is the flower of the mouth” refers to the fact that what distinguishes humans from other animals is our vocal apparatus and our mouth movements to produce unique, meaningful, ageed-upon sounds that stand for objects and ideas. We form words with the musculature of our mouths and out come sounds that could be compared to the flowers of a plant, reaching out for communication with the sun. In this case, we are reaching out to other humans and can create wonders together, as beautiful as flowers.