Our Master al-Sadiq, glorified is his glory, was asked: "What is the minimum that suffices for recognition?" He replied:

“Acknowledging that there is no god besides Him, that He has no likeness and no peer, and that He is Primordial, affirmed, existing, never absent, and that there is nothing like unto Him.”

And he, glorified is his glory, said, as recorded in Biḥār al-Anwār:

“Verily, Allah made His recognition an obligation; thus, it is indispensable for every believer to recognize his Lord so that his worship becomes sound. However, it is impossible for anyone to recognize the Essence in its utmost core reality and quiddity (al-kunh wa-l-māhiyyah). The furthest that human intellects can reach in recognizing Allah is the acknowledgment that He is a Thing, that nothing resembles Him, that He is distinct in His Essence and His attributes, that there is nothing like unto Him, and that He is Living, Competent, Hearing, Just, Generous...” etc

It is stated in the book ‘Aqā’id al-Shī‘ah:

“The monotheism of the Essence (tawḥīd al-dhāt) is to hold the doctrine that Allah is Necessary in Existence by virtue of His own Essence, declared transcendent above anthropomorphism (al-tajsīm), incarnation (al-ḥulūl), composition (al-tarkīb),