Jesus has always existed although his earthly incarnation was for only thirty-three years. In the Old Testament we find numerous examples of his appearing, known as a "Christophony". Here are several examples:
"And he said, Thou canst not see my face: for there shall no man see me, and live." - Exodus 33:20
"And it shall come to pass, while my glory passeth by, that I will put thee in a clift of the rock, and will cover thee with my hand while I pass by:
And I will take away mine hand, and thou shalt see my back parts: but my face shall not be seen. - Exodus 33:22-23
Yet a few verses back, it says that Moses spoke to God face-to-face, so how can this be?
"And the LORD spake unto Moses face to face, as a man speaketh unto his friend." - Exodus 33:11.
Well, knowing the nature of God that there are Three Person fo the Godhead, isn't it possible that God appeared at times as the Second Person, namely Jesus, rather that in all the Glory of the Father, which would consume anyone who would behold God?
"No man hath seen God at any time, the only begotten Son, which is in the bosom of the Father, he hath declared him." - John 1:18
"Not that any man hath seen the Father, save he which is of God, he hath seen the Father." - John 6:46
yet there were time when various figures, such as Moses, appeared to be talking to God face-to-face. the clue in Exodus 33:11 may be in the phrase "as a man speaketh unto his friend". So the possibility exists that God appeared in the form of a man, namely the Second Person of the Godhead.
I will give some more examples:
Shadrach, Meshach, adn Abidigo - Daniel 3:19-15:
Then was Nebuchadnezzar full of fury, and the form of his visage was changed against Shadrach, Meshach, and Abednego: therefore he spake, and commanded that they should heat the furnace one seven times more than it was wont to be heated.
And he commanded the most mighty men that were in his army to bind Shadrach, Meshach, and Abednego, and to cast them into the burning fiery furnace.
Then these men were bound in their coats, their hosen, and their hats, and their other garments, and were cast into the midst of the burning fiery furnace.
Therefore because the king's commandment was urgent, and the furnace exceeding hot, the flames of the fire slew those men that took up Shadrach, Meshach, and Abednego.
And these three men, Shadrach, Meshach, and Abednego, fell down bound into the midst of the burning fiery furnace.
Then Nebuchadnezzar the king was astonished, and rose up in haste, and spake, and said unto his counsellors, Did not we cast three men bound into the midst of the fire? They answered and said unto the king, True, O king. He answered and said, Lo, I see four men loose, walking in the midst of the fire, and they have no hurt; and the form of the fourth is like the Son of God."
This one is obvious. While three people were tossed into the furnace, a fourth one who appears as "the Son of God" is present. We all know that the Son of God is the Lord Jesus Christ.
Joshua - Joshua 5:13-15
"And it came to pass, when Joshua was by Jericho, that he lifted up his eyes and looked, and, behold, there stood a man over against him with his sword drawn in his hand: and Joshua went unto him, and said unto him, Art thou for us, or for our adversaries?
And he said, Nay; but as captain of the host of the LORD am I now come. And Joshua fell on his face to the earth, and did worship, and said unto him, What saith my Lord unto his servant? And the captain of the LORD's host said unto Joshua, Loose thy shoe from off thy foot; for the place whereon thou standest is holy. And Joshua did so."
Some obvious parallels in this one. First, it should be noted that this Captain of the Host of the Lord is neutral to the conflict. He is neither for or against Joshua and not part of the action. The figure commands Joshua to loosen his shoes off his feet for the place is holy ground, which is reminiscent of when Moses met God in the form of a burning bush and told to remove his shoes likewise. We could suppose that the figure is angel, except that Joshua falls to his face and worships the figure.
In Revelation 19:10, John fell down at the feet of the messenger that was speaking to him, but the figure there rebukes John:
"And I fell at his feet to worship him. And he said unto me, See thou do it not: I am thy fellow servant, and of thy brethren that have the testimony of Jesus: worship God: for the testimony of Jesus is the spirit of prophecy."
So the implication here is that the Captain of the Lord's Host is not an angel, but the Lord Jesus Christ, Himself.
Abraham - Genesis 18:1-3
"And the LORD appeared unto him in the plains of Mamre: and he sat in the tent door in the heat of the day;
And he lift up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground, And said, My LORD, if now I have found favour in thy sight, pass not away, I pray thee, from thy servant:"
This one is a bit trickier, but you should see in a moment how.
First, it should be noted that Abraham falls to the ground and worships in front of the three men. Why three? Let's look at later in the passage in Genesis 18:16-17.
"And the men rose up from thence, and looked toward Sodom: and Abraham went with them to bring them on the way.
And the LORD said, Shall I hide from Abraham that thing which I do; Seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him?"
You will notice that the men rose up and left for Sodom, leaving for Sodom, leaving God to talk to Moses about the fate of that city. But how many actually left?
Go to the next chapter, Genesis 19:1:
"And there came two angels to Sodom at even; and Lot sat in the gate of Sodom: and Lot seeing them rose up to meet them; and he bowed himself with his face toward the ground;"
Wait a minute! I thought there were three? What happened to the one? Could it be that the other man was the Lord Jesus Christ who was left behind to talk to Abraham about the fate of Sodom back at the end of Genesis 18?
Remember what Jesus said to the Jews who claimed Abraham as their father in John 8:56-58?
"Your father Abraham rejoiced to see my day: and he saw it, and was glad.
Then said the Jews unto him, Thou art not yet fifty years old, and hast thou seen Abraham?
Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am."