It is written, "A sun and a shield is Havayah Elokim". (Psalms 84:12) The explanation of this verse is as follows: "A shield" implies a covering of some sort that is used to protect one from the light of the sun. One shields oneself from the light so that he should be able to bear its intensity. This is reminiscent of what our Sages, of blessed memory, said: "In the Future, the Holy One will take [the light of] the sun out of its sheath [orb]. The wicked will be punished by it and the righteous will be healed...." (Nedarim 8b) For the time being, just as a sheath shields and protects us from the sun, so also does the name Elokim shield and protect us from the powerful revelation of the Blessed Havayah.... The meaning of the name Havayah itself is "mehaveh - He who constantly brings everything into existence ex nihilo". (Tanya, Shaar HaYichud Ve'ha'emuna 4)
The concept of multiplicity…does not imply a real separation….
The name Elokim is like a shield, sheath, or garment which conceals and hides within itself the life-force that emanates from Havayah - the One who constantly brings everything into existence. This then allows for the existence of finite, separate creations made up of soul [light] and body [vessel]. The soul parallels the life-force of Havayah that shines into Elokim, and the body parallels Elokim which hides and covers over Havayah. This is [the root reason] why the body is literally a garment over the soul. It is also the reason why the Torah warns us numerous times, "Know today and reflect on it in your heart that Havayah is Elokim in the heavens above and on the earth below - there is nothing else". (Deut. 4:39) This comes to teach us that the concept of multiplicity [of finite, separate existences] that comes about through the name Elokim does not imply a real separation from Havayah in any way whatsoever. Even after multiplicity is brought about via the name Elokim, all is still included in the unity of Havayah just as it was before the world was created. In truth, therefore, there is no separate existence. All is one seamless Unity.
This can be understood by way of analogy: Imagine a large barrel filled with water. In order to fill up many smaller buckets from this large barrel, we can use many tubes or pipelines [as many as there are buckets]. Of course, each tube has to limit and constrict the flow of water from the barrel to fit the size and capacity of each bucket. In this way, the water can be distributed to the various buckets - something that would be impossible if we had to pour straight from the barrel. Indeed, pouring straight from the barrel would cause great quantities of water to spill out over the sides of the small buckets [rendering the entire procedure a failure]...
These permutations are merely pipelines through which the essence life-force of Havayah flows….
Now, you can see that even though the tubes seem to have constricted the water, they are nothing more than the medium through which the water's flow is tapered off. They do not affect the water itself. In fact, as long as the water flows from the barrel through the tubes and into the buckets, it [the water] is still not separated from its source [in the barrel]. In the same way, the name Elokim, which is associated with the concept of gevura and constriction [tzimtzum], constricts the life-force of the waters of G‑d's loving-kindness [chesed]. This is alluded to in the verse, "Peleg Elokim malei mayim" - "the name Elokim differentiates [Havayah] which is full of water". (Psalms 65:10) It is also alluded to in the phrase "Lift up your eyes on high and behold Who has created these [in Hebrew, 'Mi bara eleh']!". (Isaiah 40:26) [According to the Zohar I:2a, the code-word for the world of multiplicity that we see is "these", "eleh" in Hebrew. Look at "these", and ask "Who" - "mi" in Hebrew. Combine the two words "eleh" and "mi" - "these" and "Who" - and you arrive at "Elokim".] The "mi-Who" of Elokim is the source of "eleh-these", which represents the concept of multiplicity and separate existence.
This again is the meaning of "Peleg Elokim malei mayim", namely, the name Elokim differentiates and divides via subsidiary pipelines which are the permutations of the Hebrew letters that cover over and conceal the Light of the Infinite that manifests through Havayah - He who was, He who is, and He will be forever - who is absolutely boundless and limitless, with no beginning and no end.... Behold, these permutations are merely pipelines through which the essence life-force of Havayah flows. And, as we saw above, even after it clothes itself in them, it is never separated from its source. All remains One.
Furthermore, the concealment that is brought about by the letters is only from our point of view and for our benefit. From G‑d's point of view, there is no concealment whatsoever. So it is now self-evident that even after separation and multiplicity is brought into existence via the name Elokim, all is still included in His Blessed Unity. On the contrary, the concealment only exists for us, whereas for Him, all of Creation is as naught, just as it was before He created it... And this is the mystery of "Havayah is Elokim" - there is nothing else....
[Adapted by Avraham Sutton from Derech Mitzvotecha, Mitzvat Milah, p.10]