John Webster on a constructive way into Barth’s doctrine of Scripture, and the role that testimony ought to play in a general doctrine of Scripture.
Much less likely to beguile us into such problems is a third concept, namely that of Scripture as prophetic and apostolic testimony, much used by Barth throughout his writings, but found elsewhere in Reformed theology. What makes this a particularly helpful term is the way in which it retains the human character of the biblical materials without neglect of their reference to the Word and work of God. The very genre of ‘testimony’ — as language which attests a reality other than itself — is especially fitting for depicting how a creaturely entity may undertake a function in the divine economy, without resort to concepts which threaten to divinise the text, since — like prophecy or apostolic witness — testimony is not about itself but is a reference beyond itself. However, some careful specification is needed, because the notion of Scripture as human testimony to God’s revealing activity can suggest a somewhat accidental relation between the text and revelation. This is especially the case when the essential unsuitability or creaturely fragility of the testimony is so stressed (in order to protect the purity of the divine Word) that there appears to be little intrinsic relation between the texts and the revelation to which they witness. In this way, the annexation of the Bible to revelation can appear almost arbitrary: the text is considered a complete and purely natural entity taken up into the self-communication of God. The result is a curious textual equivalent of adoptionism. If the difficulty is to be retarded, however, it has to be by careful dogmatic depiction of the wider scope of the relation between God and the text, most of all by offering a theological description of the activity of God the Holy Spirit in sanctifying all the processes of the text’s production, preservation and interpretation. Thereby the rather slender account of divine action vis-à-vis the text is filled out, without falling into the problems of undermining the creatureliness of the text which afflict talk of accommodation or the analogy of the hypostatic union.
 John Webster, Holy Scripture: A Dogmatic Sketch, 23-4.