והנה כאשר ישים המשכיל אלה הדברים אל עומקא דלבא ומוחא, אזי ממילא כמים הפנים לפנים
When the thinking person will reflect on these matters in the depths of his heart and brain, then as surely as water mirrors the image of a face,
When the love likened to "water mirroring the image of a face" takes effect in a person, so that G‑d's manifest love for His people arouses in him a corresponding love towards Him, then:
תתלהט נפשו ותתלבש ברוח נדיבה, להתנדב להניח ולעזוב כל אשר לו מנגד, ורק לדבקה בו יתברך, וליכלל באורו בדביקה חשיקה וכו׳, בבחינת נשיקין ואתדבקות רוחא ברוחא כנ״ל
his soul will spontaneously be kindled with love for G‑d, and it will clothe itself in a spirit of benevolence, willingly to lay down and resolutely to abandon all he possesses, for it will no longer be of major importance to him, in order only to cleave unto Him, and to be absorbed into His light with an attachment and longing, and so forth, in a manner of "kissing", and with an attachment of spirit to Spirit, as has been explained earlier.
Just as kissing involves not only the cleaving of mouths but also a communion of breaths, so too does spiritual unity involve the union of man's spirit with G‑d's: man's spirit becomes one with G‑d's.
אך איך היא בחינת אתדבקות רוחא ברוחא
But how does the attachment of spirit to Spirit take place? I.e., what measures are to be taken if one seeks to desire to "only cleave to Him"?
לזה אמר: והיו הדברים האלה גו׳ על לבבך, ודברת בם גו׳
To this end it is stated, soon after the phrase, "with all your heart," and so on:1 "And these words shall be... upon your heart.... And you shall speak of them...." As will soon be explained, this refers to immersing oneself in the study of Torah and speaking words of Torah.
וכמו שכתוב בעץ חיים, שיחוד הנשיקין עיקרו הוא יחוד חב״ד בחב״ד, והוא עיון התורה
As is explained in Etz Chayim, the union of "kissing" which incorporates the union of the "attachment of spirit to Spirit" is essentially the union of ChaBaD with ChaBaD — the union of man's Chochmah, Binah and Daat with G‑d's; that is, concentration in the Torah, which unites man's ChaBaD with the intellect of above, i.e., Torah,
והפה הוא מוצא הרוח וגילויו בבחינת גילוי, והיינו בחינת הדבור בדברי תורה
while the mouth, as the outlet of the breath and its emergence into a revealed state, represents the category of speech engaged in words of the Torah,
By speaking words of Torah — as it is written, "And you shall speak of them" — the spirit emerges into a revealed state. Thus, the union of "spirit with Spirit" is mainly brought about by one's immersion in Torah study. The reason for this follows:
