I can tell you about the burning bush. The burning bush was seen by Moses, and he understood that God was there. He tried to approach, and the voice of God said, Put off thy shoes from off thy feed, for the place whereon thou standest is holy ground (Ex 3:5). The bush was enveloped in Light, but the Light did not consume it. It was the same Light that God gives to man, which in touching us does not consume us. Only sin is consumed in us, as this Light gives us perfection or makes us better.
You know that this burning bush represents the Mother of God, who received in herself the absolute Light of Jesus Christ, the fire. We say in our prayers before receiving the Body and Blood of Jesus Christ: “Rejoicing and trembling at once, I who am straw partake of fire, and, strange wonder! I am ineffably bedewed, like the bush of old, which burnt without being consumed.” It is true: we take in our mouth the fire — God, Jesus Christ — but we are not burnt because the fire consumes nothing except for sin [Isa 6:1-7].
In Exodus we read: The glory of the Lord abode upon Mount Sinai, and the cloud covered it six days: and the seventh day He called unto Moses out of the midst of the cloud. And the sight of the glory of the Lord was like devouring fire on the top of the mount in the eyes of the children
of Israel (Ex 24:16-17). This means that the mountain was covered by that Uncreated Light which cannot be comprehended by us.
God said to Moses: Thou canst not see My face: for there shall no man see Me, and live…. Thou shalt see My back parts, but My face shall not be seen (ex 33:20, 23). No one can see God and be alive because we can never see or understand the Essence of God. He is above everything: above every mind, above every possibility of being misunderstood. Even the angels cannot see the face of God, that is, His Essence. They see only his “back parts,” that is, His Uncreated Energies.
What did Moses see? He saw precisely the Uncreated Light of Energies. After that, he lived: this means he did not see the face of God, but saw only His Uncreated Energies. The Holy Fathers say that we, like the angels, can only see the “back parts” of God. We can see only from the back and never see His face.
Afterwards, when Moses was invited by God to the top of Mount Sinai and wrote down the Ten Commandments, the glory of God again filled the mountain. Moses didn’t see the face of God, he saw only the Uncreated Light.
Sometimes this Light makes the body and soul come near to perfection, and thus the body begins to shine. The Light is incorporated by the body and becomes visible to the physical eyes. That is why Moses, when he came down from the mountain, covered his face with a veil: the shining of his face was unbearable for the Jews to look at (cf. Ex 34:33-35). The Uncreated Energy was present in his body, not only in his spirit.
Fr. George Calciu. Interviews, Homilies, and Talks. Platina. Saint Herman of Alaska Brotherhood. 2010. 264-265.
 Prayer of St. Symeon the New Theologian.