Tablets of Abdu'l-Baha
But as to the question of the Trinity, know, O advancer unto God, that in each one of the cycles wherein the Lights have shone forth upon the horizons (i. e., in each prophetic dispensation) and the Forgiving Lord hath revealed Himself on Mount Paran (see Habbakkuk 3:3, etc.) or Mount Sinai, or Mount Seir (see Ezekiel 35), there are necessarily three things: The Giver of the Grace, and the Grace, and the Recipient of the Grace; the Source of the Effulgence, and the Effulgence, and the Recipient of the Effulgence; the Illuminator, and the Illumination, and the Illuminated. Look at the Mosaic cycle: The Lord, and Moses, and the Fire (i. e., the burning bush), the Intermediary; and in the Mohammedan cycle: The Lord, the Apostle (or Messenger, Mohammed), and Gabriel (for, as the Mohammedans believe, Gabriel brought the Revelation from God to Mohammed). Look at the sun and its rays and the heat which results from its rays; the rays and the heat are but two effects of the sun, but inseparable from it; yet the sun is one in its essence, unique in its real identity, single in its attributes, neither is it possible that anything should resemble it. Such is the essence of the Truth concerning the Unity, the real doctrine of the Singularity, the undiluted reality as to the (Divine) Sanctity.