For how shall we be able to know, I and thy people, that we have found grace in thy sight, unless thou walk with us, that we may be glorified by all people that dwell upon the earth? And the Lord said to Moses: This word also, which thou hast spoken, will I do: for thou hast found grace before me, and thee I have known by name. And he said: shew me thy glory. He answered: I will shew thee all good, and I will proclaim in the name of the Lord before thee: and I will have mercy on whom I will, and I will be merciful to whom it shall please me. And again he said: Thou canst not see my face: for man shall not see me and live. (Exodus 33, 16-20 - from the first prophecy of Great Friday Vespers)