The human body is a mandala of letters - because of that, people are able to understand the meaning of Dharma

Where does sound come from? That’s a question. According to Vajrayana all the sounds, the source of all the sounds in phenomena is from letters or from syllables. And our sound language is based on the letters. So when you are reborn as a Vietnamese, then Vietnamese alphabet, the letters appear in the first place in your body, in your channels in your body. Because of that you are able to talk, to speak loudly. You have the sound and the meanings. You are able to describe things.

Not only that but also we believe that [happens] in [others] like animals. Even though they cannot talk but they have sound, because there’re some, very simple, syllables, some letters that also exist in their channels. For that reason, every sentient being has its own sound or language. There’re hundreds or thousands of syllables in our body. And in the Sutra, in the Tantra-yana it is said that the body of human body is a mandala of letters. Because of that, people are able to understand the meaning of Dharma. Because the source of Dharma, the source of our understanding is inside. It’s not something external, separated, from us but it’s inside things. Therefore, this source of the seed of understanding, of chanting, of talking languages is inside things.

 Hungkar Dorje Rinpoche, “GURU YOGA: The Source of Power in Speech and The Purification”