Essence of God

From the Writings of Baha'u'llah:
Regard thou the one true God as One Who is apart from, and immeasurably exalted above, all created things. The whole universe reflecteth His glory, while He is Himself independent of, and transcendeth His creatures.
    (Baha'u'llah: Gleanings, p. 166)

For God is, in His Essence, holy above ascent and descent, entrance and exit; He hath through all eternity been free of the attributes of human creatures, and ever will remain so.
    (Baha'u'llah: Seven Valleys and Four Valleys, pp. 22-23)

To every discerning and illumined heart it is evident that God, the unknowable Essence, the divine Being, is immensely exalted beyond every human attribute, such as corporeal existence, ascent and descent, egress and regress. Far be it from His glory that human tongue should adequately recount His praise, or that human heart comprehend His fathomless mystery. He is and hath ever been veiled in the ancient eternity of His Essence, and will remain in His Reality everlastingly hidden from the sight of men.
    (Baha'u'llah: The Kitab-i-Iqan, p. 98)

He, in truth, hath, throughout eternity, been one in His Essence, one in His attributes, one in His works. Any and every comparison is applicable only to His creatures, and all conceptions of association are conceptions that belong solely to those that serve Him. Immeasurably exalted is His Essence above the descriptions of His creatures. He, alone, occupieth the Seat of transcendent majesty, of supreme and inaccessible glory. The birds of men's hearts, however high they soar, can never hope to attain the heights of His unknowable Essence. It is He Who hath called into being the whole of creation, Who hath caused every created thing to spring forth at His behest. Shall, then, the thing that was born by virtue of the word which His Pen hath revealed, and which the finger of His Will hath directed, be regarded as partner with Him, or an embodiment of His Self? Far be it from His glory that human pen or tongue should hint at His mystery, or that human heart conceive His Essence.
    (Baha'u'llah: Gleanings, p. 193)

Every attempt which, from the beginning that hath no beginning, hath been made to visualize and know God is limited by the exigencies of His own creation - a creation which He, through the operation of His own Will and for the purposes of none other but His own Self, hath called into being. Immeasurably exalted is He above the strivings of human mind to grasp His Essence, or of human tongue to describe His mystery. No tie of direct intercourse can ever bind Him to the things He hath created, nor can the most abstruse and most remote allusions of His creatures do justice to His being.
    (Baha'u'llah: Gleanings, p. 318)

From the Writings and Utterances of `Abdu'l-Baha:
But that Essence of Essences, that Invisible of Invisibles, is sanctified above all human speculation, and never to be overtaken by the mind of man. Never shall that immemorial Reality lodge within the compass of a contingent being. His is another realm, and of that realm no understanding can be won. No access can be gained thereto; all entry is forbidden there. The utmost one can say is that Its existence can be proved, but the conditions of Its existence are unknown.
    (`Abdu'l-Baha: Selections ... `Abdu'l-Baha, p. 54)

Then how could it be possible for a contingent reality, that is, man, to understand the nature of that pre-existent Essence, the Divine Being? The difference in station between man and the Divine Reality is thousands upon thousands of times greater than the difference between vegetable and animal. And that which a human being would conjure up in his mind is but the fanciful image of his human condition, it doth not encompass God's reality but rather is encompassed by it. That is, man graspeth his own illusory conceptions, but the Reality of Divinity can never be grasped: It, Itself, encompasseth all created things, and all created things are in Its grasp. That Divinity which man doth imagine for himself existeth only in his mind, not in truth.
    (`Abdu'l-Baha: Selections ... `Abdu'l-Baha, p. 47)

God is pure perfection, and creatures are but imperfections.
    (`Abdu'l-Baha: Some Answered Questions, p. 113)

Nevertheless, we speak of the names and attributes of the Divine Reality, and we praise Him by attributing to Him sight, hearing, power, life and knowledge. We affirm these names and attributes, not to prove the perfections of God, but to deny that He is capable of imperfections. When we look at the existing world, we see that ignorance is imperfection and knowledge is perfection; therefore, we say that the sanctified Essence of God is wisdom. Weakness is imperfection, and power is perfection; consequently, we say that the sanctified Essence of God is the acme of power. It is not that we can comprehend His knowledge, His sight, His power and life, for it is beyond our comprehension; for the essential names and attributes of God are identical with His Essence, and His Essence is above all comprehension.
    (`Abdu'l-Baha: Some Answered Questions, p. 148)

The knowledge of the Reality of the Divinity is impossible and unattainable, but the knowledge of the Manifestations of God is the knowledge of God, for the bounties, splendors and divine attributes are apparent in Them. Therefore, if man attains to the knowledge of the Manifestations of God, he will attain to the knowledge of God; and if he be neglectful of the knowledge of the Holy Manifestations, he will be bereft of the knowledge of God.
    (`Abdu'l-Baha: Some Answered Questions, p. 222)

From the Writings of Shoghi Effendi:
God is the Infinite Essence, the Creator. We cannot picture Him or His state, but if we did, we would be His equals, not His creatures.
    (Shoghi Effendi: High Endeavors, p. 70)