Likutei Moharan 55:5/ליקוטי מוהר"ן נ״ה:ה׳

15. This is the aspect of dust and ashes mentioned in connection with the [red] cow. The aspect of prayer requires the aspect of dust and ashes. For both in the particular and in the general, a person must subdue the evil to the good, in the aspect of “You will crush the wicked, for they will be ashes under the soles of your feet” (Malakhi 3:21). This is the aspect of ashes within the aspect of prayer. And foot is the aspect of prayer, as in (Psalms 26:12), “My foot stood….”

2The evil in the particular—i.e., his physical body and his corporeality—he should nullify during prayer; like the early chassidim, who while praying divested themselves of all corporeality. And the evil in the general—i.e., the prayers he prays with the Jewish sinners—he should nullify their evil. He should turn the evil into a buttress for holiness. This is the aspect of the ashes in prayer.

3As for the dust in prayer—this entails binding himself, in general and in particular, with the nefesh - ruach - neshamah of those who rest in the dust, and through his prayers arouse them to pray with him in the aspect of “Awake and sing out, you who rest in the dust” (Isaiah 26:19). This is the meaning of “Let him put his mouth to the dust” (Lamentations 3:29)—i.e., he should bind his words to those who rest in the dust, as explained above.

4This is what Avraham prayed, “I have begun to speak up before my Lord, and I am mere dust and ashes” (Genesis 18:27)—because this is a necessary element for the aspect of prayer.

5And this is called praying with a quorum, because the letters TZiBuR (quorum) are the acronym of TZaddikim Beinonim Reshaim (the righteous, the intermediate, the wicked). “The intermediate” is the one praying, as in the teaching of the Sages (Kiddushin 40b): A person should always consider himself as if his merits [and offenses] are equally balanced. “The tzaddikim” are the aspect of dust; “the wicked” are the aspect of ashes, as explained above.

6Awakening those who rest in the dust—this applies in the particular and in the general. The particular is the parts of his nefesh - ruach - neshamah that were already reincarnated and rectified. The general is the nefesh - ruach - neshamah of others resting in the dust, to rouse them to pray with him.

7This is also the aspect of the many sevens associated with the [red] cow; whatever relates to it is seven, as is brought (Zohar III, 76b): seven washings, seven priests, etc. This is the aspect of prayer, corresponding to “I praise You seven times daily” (Psalms 119:164) .