He was referring to that which is perfect (complete). With the New Testament, we are no longer looking through a glass darkly when it comes to reading and studying out the Old Testament. However, when Paul wrote 1 Corinthians (one of the earliest NT books written) the OT was not opened up completely yet. Now we have Hebrews and other NT passages to open up the OT types and shadows - therefore we are seeing Jesus face to face in the Scriptures.