The Old Testament is full of imagery of Jesus. Much of the temple imagery is based upon what would later be fulfilled by Jesus.
All through the Old Testament the bible is filled with prophecy of Jesus.
I have heard some people say that the most powerful apologetic for Christianity is explaining the Old Testament prophecy related to Jesus. I agree with this point.
It is often a far more helpful apologetic to unfold the Old Testament prophecy regarding the coming Messiah than to argue solely by reason. You see reason is heavily influenced by emotion. We often only accept what pleases us.
The Old Testament prophecy regarding the Messiah is more powerful for various reasons. First it bypasses human reason in the sense that we meet something we cannot explain by human reason. We meet God telling us what will happen if we have ears to hear.
Also we meet in the bible an appealing reason to accept God. If we truly understand who God is then we will desire to accept him.