O Salman!

O Salman! The door of the knowledge of the Ancient Being hath ever been, and will continue for ever to be, closed in the face of men. No man's understanding shall ever gain access unto His holy court. As a token of His mercy, however, and as a proof of His loving-kindness, He hath manifested unto men the Day Stars of His divine guidance, the Symbols of His divine unity, and hath ordained the knowledge of these sanctified Beings to be identical with the knowledge of His own Self.
Whoso recognizeth them hath recognized God. Whoso hearkeneth to their call, hath hearkened to the Voice of God, and whoso testifieth to the truth of their Revelation, hath testified to the truth of God Himself. Whoso turneth away from them, hath turned away from God, and whoso disbelieveth in them, hath disbelieved in God. Every one of them is the Way of God that connecteth this world with the realms above, and the Standard of His Truth unto every one in the kingdoms of earth and heaven. They are the Manifestations of God amidst men, the evidences of His Truth, and the signs of His glory.

Gleanings From the Writings of Bahá’u’lláh