At Matan Torah God revealed himself.
The Jew’s literally saw, how all was God and there is nothing else.
It is well know the teaching of the Baal Shem Tov that everything that occurs is God guidance – and this is certainly the case with the entire Torah.
In fact all the laws / Mitvos are guidance.
The heavenly realm reacts to the earthly (for example, when a Jew feels the giving of the Torah on Shavous, this causes it.)
The mechanism that God used to show the Jewish people Himself, was the dew of Torah (which came on Matan Torah) and this dew comes every Shavous, and in fact can invigorate at all times.
When man humbles himself (which means not that we break ourselves but humble, as the famous saying, “there is nothing more whole than a broken heart”) this causes a reciprocation from God.
DIVINE RAIN – DEW
The above is like rain (which first needs evaporated water – but then there is a Divine gift (namely dew.)
The rain of Torah is the revealed part and hence is reciprocally granted based on the effort man puts in, but the dew is the Chassidus which is both a Divine gift, beyond what we earned (though it comes after we sow to say plowed the field, through the revealed part) and it penetrates (seeps) everywhere.
As the Dew of the Torah descended at Mount Sinai as the Alter Rebbe indicates, it currently is accessible.
DIVINE DEW – MATAN TORAH
The whole point of Matan Torah was that this dew should come within, internalized and transform through Divine (continual) wisdom.
DIVINE DEW – MOSHE DOVID BAAL SHEM TOV REBBES
The dew of Torah, though given by Moshe was concealed and the beginning of its revelation was with Dovid, but its complete revelation began with the Baal Shem Tov, and continued with the Rebbes (and obviously will be completed by Moshiach.)