Jesus has been with us and for us since Day 1:
For by Him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by Him, and for Him:
Colossians 1:16
In the Old Testament, “angel” has multiple meanings – the normal “angel” that we think of when we hear the word – God’s servants. “Messenger” is another typical meaning. However, there are instances where it is specifically referring to Jesus as God (not the normal angelic messenger that we think of when we see it in the Bible):
And the Angel of God spake unto me in a dream, saying, Jacob: And I said, Here am I.
Genesis 31:11,13
I am the God of Bethel, where thou anointedst the pillar, and where thou vowedst a vow unto Me: now arise, get thee out from this land, and return unto the land of thy kindred.
Here we see “the Angel of God” speaking to Jacob in a dream in verse 11. Two verses later, we find out it is actually God, in this case Jesus, speaking to Jacob.
And the Angel of the LORD appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed.
Exodus 3:2
And when the LORD saw that he turned aside to see, God called unto him out of the midst of the bush, and said, Moses, Moses. And he said, Here am I.
Exodus 3:4
Here we see the “Angel of the Lord” in the midst of the bush in verse 2, and verse 4 elaborates further and says it’s actually God (in this case, Jesus), since He called Moses “out of the midst of the bush”. Who was in the midst of the bush? The Angel of the Lord (verse 2), which was God (verse 4).