וַיֹּאמֶר יְ־הֹוָ־ה אֶל מֹשֶׁה אֱמֹר אֶל הַכֹּהֲנִים בְּנֵי אַהֲרֹן וְאָמַרְתָּ אֲלֵהֶם לְנֶפֶשׁ לֹא יִטַּמָּא G!d said to Moses, “Speak to the Kohanim, the sons of Aaron, saying to them, ‘None shall defile himself.'” Leviticus 21:1
As the Zohar teaches, there are four worlds: Atzilut (Emanation), Briah (Creation), Yetzirah (Formation), and Assiyah (Action) (1). Each one has an aspect of life, and also the opposite (God forbid!). We see for ourselves how in the world of Assiyah there is both life and its opposite (2). Likewise in the world of Yetzirah, which is the world of Speech (3): when a person speaks idle words this is called the opposite, and when a person speaks good words, of Torah, mitzvot, and service of the Creator, this is the aspect called life. This is hinted at in the verse from Proverbs, “Death and life are in the power of the tongue” (4). The most important thing in serving God is to guard your speech. Likewise in the world of Briah, which is the world of Thought, the aspect of life comes from when a person thinks always of how to serve God, but if not, then its opposite. And there is a world higher than these, the world of Awe, in which all existence is nullified [in God] (5), and there too exist both life and its opposite. But the most important is Speech — that you guard your speech, for everything depends on it. And this is what is being hinted at in our verse, Speak to the Kohanim…saying to them, ‘None shall defile himself.’
1) See Zohar Hadash, Yitro 34a 2) Assiyah is the world closest to our material world, here I believe even identified with our world. 3) Likutei Torah, Bereishit 4) 18:21 5) That is, the world of Atzilut, which also means “Closeness.” It is the world closest to the Ayn Sof, the Infinite One; being that close to pure divinity overwhelms all sense of separateness and identity, and one is left with nothing but a feeling of awe.
I don’t know about you, but I’d say 99% of my sins come out of my mouth. The Berditchever, ever the pragmatist, must have seen the same thing. So his advice is to come down out of the spiritual clouds and just pay attention to what we’re saying. Get that right, and you’re almost there.