Here are excellent resources concerning the view of the early Church regarding Scripture.
Formal Sufficiency of Scripture
Stated and Examined from Scripture and the Fathers, with scholarly confirmation regarding the Fathers’ views.
In an introduction section, we discussed the nature of formal sufficiency that we, the Reformed, affirm. In the next section, we saw Scripture’s own testimony to its own sufficiency. If we were simply establishing the Reformed position, that would be completely sufficient. It would not be necessary to add anything to that.
Nevertheless, our challenger from the Roman side has requested some patristic confirmation. Frankly, we are not sanguine about the possibility that he’ll actually carefully read and consider the evidence that we present, yet perhaps these evidences will be sufficient to help establish that our insight into Scripture is not a novel insight.