I just came across this helpful quote from Augustine while reading David L. Baker, Two Testaments, One Bible: The Theological relationship Between the Old and New Testaments (IVP, 2010, p. 38):
To the Old Testament belongs more fear
just as to the New Testament more delight;
nevertheless in the Old Testament the New lies hid,
and in the New Testament the Old is exposed.
This more famously comes to us in the poetic form,
The New is in the old concealed,
the Old is in the New revealed.
While Augustine is not infallible, I think he really got it right with this one.