The New Testament is in the Old Testament concealed; the Old Testament is in the New Testament revealed

To borrow a line from Chuck Missler ‘The New Testament is in the Old Testament concealed; the Old Testament is in the New Testament revealed.’
The Old Testament is not only for the Jews to believe in. Believing in Jesus Christ as the Messianic Saviour, as Christians do, is absurd without the foundation of the Old Testament.
Why would you believe in a guy who says he is the Saviour without any authentication?
Jesus’ authentication is found in the Old Testament.

There are over 300 Messianic Prophecies concerning Jesus Christ. No one else fits.

Jesus went to great lengths to claim himself as the Messiah by continually putting himself in context with the Old Testament. For example, when Jesus went to the Synagogue in his home town of Nazareth, he read from an Old Testament prophecy (Isaiah 61). Jesus read:

The Spirit of the Lord is on me,
because he has anointed me
to preach good news to the poor.
He has sent me to proclaim freedom for the prisoners
and recovery of sight for the blind,
to release the oppressed,
to proclaim the year of the Lord's favor."[e]

Then he rolled up the scroll, gave it back to the attendant and sat down. The eyes of everyone in the synagogue were fastened on him, and he began by saying to them, "Today this scripture is fulfilled in your hearing." (Luke 4)

The actual prophecy he was reading from is in Isaiah:

The Spirit of the Lord GOD is upon me; because the LORD hath anointed me to preach good tidings unto the meek; he hath sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to them that are bound; to proclaim the acceptable year of the LORD, and the day of vengeance of our God, to comfort all who mourn." -Isaiah 61:1-2

On a side note, it is interesting why Jesus stopped part way through verse 2. He didn’t read ‘and the day of vengeance of our God, to comfort all who mourn’. To me, this indicates that the day of righteous judgement (or Jesus’ Second Coming’) is still yet to come. Jesus’ first appearance was to bring the good news of Salvation. His Second will be as righteous judge.

A couple of other examples:
In John 5 Jesus said:
"...the very work that the Father has given me to finish, and which I am doing, testifies that the Father has sent me. 37And the Father who sent me has himself testified concerning me. You have never heard his voice nor seen his form, 38nor does his word dwell in you, for you do not believe the one he sent. 39You diligently study[c] the Scriptures because you think that by them you possess eternal life. These are the Scriptures that testify about me, 40yet you refuse to come to me to have life. 43I have come in my Father's name, and you do not accept me...’ 45"But do not think I will accuse you before the Father. Your accuser is Moses, on whom your hopes are set. 46If you believed Moses, you would believe me, for he wrote about me. 47But since you do not believe what he wrote, how are you going to believe what I say?"

In Matthew 26 when the Disciples tried to stop Jesus being arrested he said:
54...But how then would the Scriptures be fulfilled that say it must happen in this way?"

In Luke 18 when Jesus was preparing to be crucified he said:
"We are going up to Jerusalem, and everything that is written by the prophets about the Son of Man will be fulfilled. 32He will be handed over to the Gentiles. They will mock him, insult him, spit on him, flog him and kill him. 33On the third day he will rise again."

And in Luke 22:37
‘what is written about me is reaching its fulfilment’


In Luke 24
And after Jesus was resurrected, he hooked up with some believers along the road to Emmaus:
25He said to them, "How foolish you are, and how slow of heart to believe all that the prophets have spoken! 26Did not the Christ[b] have to suffer these things and then enter his glory?" 27And beginning with Moses and all the Prophets, he explained to them what was said in all the Scriptures concerning himself.

and what is all this for?

Acts 10:43
“All the prophets testify about him that everyone who believes in him receives forgiveness of sins through his name."