Daily Tanya Mrs. Tsyrl Turen

The epistle that follows, beginning “The letters that are revealed,” is one of the epistles that was appended to the edition of the Tanya published in Vilna in the year 5660 (1900), these additions being noted by R. Asher of Nikolayev in his introductory declaration there.53
This relevance of this epistle to the previous one may be found in the following parallel: The previous epistle explains how only the netzach-hod-yesod-malchut (i.e., the lower sefirot) of the Emanator extend to the recipient. The conclusion of the present epistle likewise explains54 that only the hindmost aspect and externality of the netzach-hod-yesod of the higher realm enter the lower one.

Surprisingly, the Hebrew verb used here is tamnu (in the first person plural), which would make the phrase mean, “we have not been brought to an end.” If the verse sought to say that the kindnesses “have not ended,” rather than “because of G-d’s kindnesses, we have not been brought to an end,” it should surely have used the verb tamu (in the third person plural), as the Alter Rebbe goes on to point out.

Hence, the Alter Rebbe will now continue, it is only the G-dliness in a “contracted” ChaBaD that creatures of Beriah can grasp and absorb (and even then only to the extent of their limited capacity); the light of ChaBaD in its pristine state, as in Atzilut, is beyond them.

Since the entire dynamic of the holy “side” of the universe has its counterpart in the “other side,” the sitra achara, the abovementioned ten sefirot of holiness (and likewise the ten corresponding faculties of the G-dly soul) each have their unholy counterpart:

Since everything is in G-d’s hands, there is no reason to become angry. However, with regard to matters involving the “fear of heaven,” anger does have a place.

The Alter Rebbe upholds that all things are sourced in the Shechina. However, untderstanding that this may be arguable contends that it "is impossible to explain this clearly in writing, only orally to an ear that hears [and understands], to uniquely qualified individuals ..."