Sola Scriptura II.
The infallible rule of intepretation of Scripture, is the Scripture itself; and therefore, when there is a question about the true and full sense of any scripture (which is not manifold, but one), it may be searched and known by other places that speak more clearly.
The Supreme Judge, by which all controversies of religion are to be determined, and all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits, are to be examined, and in whose sentence we are to rest, can be no other but the Holy Spirit speaking in the Scripture.
From Chapter 1 of the Westminster Confession.
Wherefore we do not despise the interpretations of the holy Greek and Latin fathers, nor reject their disputations and treatises concerning sacred matters as far as they agree with the Scriptures; but we modestly dissent from them when they are found to set down things differing from, or altogether contrary to, the Scriptures. Neither do we think that we do them any wrong in this matter; seeing that they all, with one consent, will not have their writings equated with the canonical Scriptures, but command us to prove how far they agree or disgree with them, and to accept what is in agreement and to reject what is in disagreement.
And in the same order also we place the decrees and canons of councils.
Wherefore we do not permit ourselves, in controversies about religion or matters of faith, to urge our case with only the opinions of the fathers or decrees of councils; much less by received customs, or by the large number of those who share the same opinion or by the prescription of a long time. Therefore, we do not admit any other judge than God himself, who proclaims by the Holy Scriptures what is true, what is false, what is to be followed, or what to be avoided.
From Chapter II of the Second Helvetic Confession