My words are like fire, says the Lord
Said Rabbi Yosef Yitzchok of Lubavitch on why Torah is compared to fire:
(a) Fire consumes and annihilates. (b) Fire sheds light and warmth upon its surroundings. (c) When fire burns in one place, it may suddenly flare up in another, especially if there is a bit of wind. (d) Fire generates fear. (e) Fire reveals the truth that the physical reality is of no substance: See, it says, how quickly all is gone!
So it is with Torah: (a) Torah annihilates the evil in one’s heart. (b) Torah sheds light and warmth upon its surroundings. (c) When Torah is studied and observed by one individual or community, it catches on in others – especially if there is a whiff of its inner spirit. (d) Torah generates the fear of Heaven (yirat shamayim). (e) Torah reveals the truth: the material world is nothing, G-dliness is the only true reality.
 In Hebrew, the word ruach means both “wind” and “spirit.”