According to Johannes Calvin, all through the Old Testament Jesus was known. How mind-boggling but - when you think about it - utterly obvious is this! The impacts of this revelation on my view of the living God are huge. But let me explain...
The evidence for the gospel to have been there from creation (and, according to Calvin, creation being "the theatre of the gospel") lies in the fact that God doesn't have a plan B. Often, the story of salvation is presented thus: in the Old Testament, the people of Israel had the law and were saved by works; in the New Testament, people are saved by faith. But doesn't Galatians 3:11 say,
"it is evident that no one is justified before God by the law, for 'The righteous shall live by faith.'"
Not even Abraham did anything to earn God's favour - Romans 4:3:
“Abraham believed God, and it was counted to him as righteousness.”
There was grace in the OT, too - grace that looked forward to the incarnation of Jesus. Yet, Jesus as part of the Trinity, has always been there. He has many names in the Old Testament. He is the Word of God, the Voice of God, the Angel of God, the Presence, etc (see also John 1 for evidence). So, as early as Genesis 3:8 we can see Jesus come and meet with the fallen humans -
"And they heard the sound of the Lord God walking in the garden in the cool of the day, and the man and his wife hid themselves from the presence of the Lord God among the trees of the garden." (see Matthew 26:36-43 for beautiful parallel)
Another instance is Genesis 15, when it says
"And behold, the word of the Lord came to him: “This man shall not be your heir; your very own son shall be your heir.” And he brought him outside and said, “Look toward heaven, and number the stars, if you are able to number them.” Then he said to him, “So shall your offspring be.”"
Abraham here actually trusts the SON - He is indeed the Mediator even as early as this in salvation history!
Genesis 16 speaks of the angel of the Lord coming to speak to Hagar. 'Angel' in Hebrew actually means 'messenger' - and can well be used of Christ. A good indication of the angel being Christ is when he accepts worship - whereas the angels = spiritual beings (like in Revelation) do not.
The implications of Exodus 3, and God=Jesus speaking from the burning bush, are massive.
"God said to Moses, “I am who I am.” ...‘The Lord, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you.’"
If Jesus says of Himself that He is the God of Abraham, Isaac and Jacob, it really is God incarnate who later died for us!!
In John 1:18, facts are pretty clear -
"No one has ever seen God; the only God, who is at the Father's side, he has made him known."
No one has seen God, not even Moses, of whom it is said in Exodus 33 -
"Thus the Lord used to speak to Moses face to face, as a man speaks to his friend."
Face to Face. Even though a little later he can't see the face of God? (But,” he said, “you cannot see my face, for man shall not see me and live.”) It must be Jesus, showing the Father, sitting on the Arc of the Covenant.
Now imagine - Jesus sits there and sees the priest make their offering of animals year in year out - all the while knowing that finally, He Himself will be offered as a blood sacrifice to terminate this process.
This makes me shiver in awe. Abraham is actually my brother... these people are indeed my "cloud of witnesses" (Hebrews 12:1) because they knew Jesus!