“And I exhort you to do nothing out of strife, but according to the doctrine of Christ. When I heard some saying, ‘If I do not find it in the ancient Scriptures, I will not believe the Gospel’; on my saying to them, It is written, they answered me, ‘That remains to be proved.’ But to me Jesus Christ is in the place of all that is ancient: His cross, and death, and resurrection, and the faith which is by Him, are undefiled monuments of antiquity; by which I desire, through your prayers, to be justified” (8:2).
The argument is that those who are saying, “If I do not find it in the ancient Scriptures, I will not believe the Gospel” are using the logic of sola Scriptura that we should only believe that which we find in Scripture. Because Ignatius is in disagreement with them, he disagrees with their assertion that we should only believe what we find in the Scriptures and instead points to the historical evidence of Christ’s resurrection. Hence, the people who disagreed with Ignatius are proto-Protestants who only believed Scripture while Ignatius appeals to Scripture and the testimony of history which now includes the ecumenical councils and other traditions.
But to understand what Ignatius is saying, we need to understand who he is talking to. He is not talking to gnostics who claimed to be following Jesus, but to Jews who did not want to believe the gospel message. The Jews only accepted the Old Testament and rejected the New Testament. That is why they demanded to see evidence for the gospel from the “ancient Scriptures.” The Greek term translated as “ancient Scriptures” is archeion which is being used to refer to ancient documents. In fact, our English word “archives” is a cognate of archeion. That they have in mind the Old Testament Scriptures alone is the consensus among scholars of the early church. The reason why they demanded evidence from the Old Testament alone is because they rejected the New Testament as Scripture. In order for critics of sola Scriptura to use Ignatius’ words against Protestantism, they must be able to prove that the archeion includes the New Testament as well.
Ignatius responds to their demand not by appealing to an unwritten oral tradition, but by going to the Old Testament to demonstrate that Jesus is the Messiah. When they disagree with his interpretation of the Old Testament, he then appeals to the historical testimony of the death and resurrection of Christ. The account of the resurrection is not an unwritten oral tradition parallel to Scripture, but the testimony of Scripture itself (1 Cor 15:3-8). Ignatius does not start by appealing to Scripture and then to oral tradition, but by appealing to the testimony of the Old Testament concerning the Messiah and then to the New Testament’s testimony concerning him. It is not Scripture and tradition that is his authority, but the Old Testament and New Testament together which make the canon complete."