Likutei Moharan 31:7/ליקוטי מוהר"ן ל״א:ז׳

17. And know! it is not enough for a person to just long in [his] heart. He has to express his yearnings orally. To this end, the prayers were established.

2As a result of the longing in the heart, a soul and vowel points are made in potential. Then, when he expresses his yearning orally, the soul is actualized. For the soul comes forth primarily from his mouth, as in (Song of Songs 5:6), “My soul came forth when he spoke.” And because of this, “seek Torah from his mouth.” Specifically from “his mouth.”

3In addition, “The man became a living soul” (Genesis 2:7) is translated into Aramaic as “a speaking spirit.” This is because the soul is essentially from speech.