God, the unknowable Essence

To every discerning and illuminated 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. “No vision taketh in Him, but He taketh in all vision; He is the Subtile, the All-Perceiving.”…
The door of the knowledge of the Ancient of Days being thus closed in the face of all beings, the Source of infinite grace, according to His saying, “His grace hath transcended all things; My grace hath encompassed them all,” hath caused those luminous Gems of Holiness to appear out of the realm of the spirit, in the noble form of the human temple, and be made manifest unto all men, that they may impart unto the world the mysteries of the unchangeable Being, and tell of the subtleties of His imperishable Essence.

Gleanings From the Writings of Bahá’u’lláh P.47