The Church had the authority to interpret the Scripture, since she was the only authentic depository of Apostolic kerygma. This kerygma was unfailingly kept alive in the Church, as she was endowed with the Spirit.
The Church was still teaching viva voce, commending and furthering the Word of God. And viva vox Evangelii [the living voice of the Gospel] was indeed not just a recitation of the words of the Scripture. It was a proclamation of the Word of God, as it was heard and preserved in the Church, by the ever abiding power of the quickening Spirit.
Apart from the Church and her regular Ministry, “in succession” to the Apostles, there was no true proclamation of the Gospel, no sound preaching, no real understanding of the Word of God. And therefore it would be in vain to look for truth elsewhere, outside of the Church, Catholic and Apostolic.
This was the common assumption of the Ancient Church, from St. Irenaeus down to Chalcedon, and further. St. Irenaeus was quite formal at this point. In the Church the fullness of truth has been gathered by the Apostles: plenissime in eam contulerint omnia quae sunt veritatis [lodged in her hands most copiously are all things pertaining to truth (Adv. Haeres., III.4.1)].
Indeed, Scripture itself was the major part of this Apostolic “deposit.” So was also the Church. Scripture and Church could not be separated, or opposed to each other. Scripture, that is— its true understanding, was only in the Church, as she was guided by the Spirit.
Origen was stressing this unity between Scripture and Church persistently. The task of the interpreter was to disclose the word of the Spirit: hoc observare debemus ut non nostras, cum docemus, led Sancti Spiritus sententias proferamus [we must be careful when we teach to present not our own interpretation but that of the Holy Spirit (in Rom. 1.3.1)]. And this is simply impossible apart from the Apostolic Tradition, kept in the Church.