Rain and Dew Rectification

יערף כמטר לקחי הוא תיקון הגוף שיש דברי תורה שמיוחדין לזה לרכך הלב להיות ראוי לקבל זריעה

"My teaching shall drip like rain" (Devarim 32:2) refers to the rectification of the body, for there are words of Torah that are designated specifically for this purpose: to soften the heart so that it should be fit to receive the planting.

The image of Torah as rain that falls and softens the ground represents the work of refining the physical body, softening a hardened heart so that it becomes receptive ground in which Torah and kedushah can take root.

והוא בחי' ימי המעשה

And this corresponds to the aspect of the weekdays, the days of action.

This rain-like dimension of Torah belongs to the weekdays, the ordinary days of action and effort, when a person must labor to make himself fit.

תזל כטל הוא בש"ק תיקון הנפש לקבל הארה מנשמה יתירה:

"It shall flow like dew" (Devarim 32:2) refers to Shabbos Kodesh, the rectification of the soul, to receive the illumination from the neshamah yeseirah, the additional soul.

Dew, by contrast, descends gently from above without being summoned, and this represents Shabbos, when the rectification reaches the neshamah itself through the illumination of the extra soul that Hashem grants on Shabbos.

Summary: The Sfas Emes draws on the verse in Ha'azinu, "My teaching shall drip like rain, my speech shall flow like dew" (Devarim 32:2), to distinguish two modes of receiving Torah. Rain corresponds to the rectification of the body: certain words of Torah are designated to soften the heart and make a person fit to receive the planting of kedushah, and this labor belongs to the weekdays, the days of action. Dew, which descends gently from above, corresponds to Shabbos Kodesh and the rectification of the soul, when a person receives illumination through the neshamah yeseirah, the additional soul granted on Shabbos. Thus the weekday avodah prepares the vessel through effort below, while Shabbos brings a higher light that flows down on its own to the neshamah.