Why travel to see a tzaddik (a righteous person) in person when you can read their teachings in a book? Rabbi Nachman of Breslov answered this question directly: there is an immeasurable difference between hearing Torah from the mouth of the true tzaddik and reading the same words on a page.
The Zohar states: "As long as there was no scale, there was no providence face to face" (Zohar II:176b). Face-to-face encounter is qualitatively different from any transmission at a distance. Each time a teaching passes from one person to another, from the original teacher to a student to a student's student, it descends from level to level. It loses radiance. A book is even more removed.
But with the tzaddik himself, something else happens entirely. The tzaddik possesses a pure countenance, a face that functions like a mirror. When you look into the face of the tzaddik, you see yourself. Not your self-image. Your actual spiritual state. And seeing the gap between the radiance of the tzaddik's face and the darkness of your own condition, you feel remorse spontaneously. No rebuke is necessary. No reproach. The face does the work.
This luminous countenance comes from the Holy Tongue, the Hebrew language with which the world was created. The Talmud derives this from the verse, "This one shall be called woman because from man was she taken" (Genesis 2:23), a wordplay that only works in Hebrew, proving that Hebrew was the language of creation (Bereishit Rabbah 18:4).
The Holy Tongue has power over all other languages. Through it, the evil embedded in the seventy nations' tongues is vanquished. The comprehensive evil that all seventy tongues share, the burning desire for sexual immorality, is nullified by the sanctity of Hebrew speech. The tzaddik who speaks Torah in the Holy Tongue does not merely convey information. He sweetens harsh decrees for everyone who hears him.