If Jesus wasnt born until the new Testament, why is it important to read the old Testament?

Answer 1

3 reasons among others:

1) the New Testament is what the Old Testament announced

Jeremiah 31:31

The New Covenant

³¹ “Behold, the days are coming, declares the Lord, when I will make a new covenant with the house of Israel and the house of Judah

2 Jesus said He was sent only to the house of Israel

 “I was sent only to the lost sheep of the house of Israel.”

And why was that? Because you have to know the basics (the OT) to graphs the New

3) Most obviouis of all, because it is the word of God and therefore of enduring value

Answer 2

Maybe the best way to understand this is to use an example of today, i.e. "Lord of the Rings." While one can see "The Return of the King" and appreciate it as a great movie (or book) but how much more would our understanding of that movie be if we had seen "The Fellowship of the Ring" and "The Two Towers." Just one example: Aragorn is not revealed as the heir (or at least one able or willing to fill that role) to the kingdom until the Return. Similarly, Jesus's identity is revealed slowly, through the prophesies in the Old Testament.