I've come at this topic "at sundry times and in divers manners," including here, here, and here, among many others.
Sunday was part three of our Thinking Biblically series at CBC, and the sufficiency of Scripture was one of the foci of the sermon titled What Should We Do with the Bible? (That and, well, once again too many other things.) I'll lift out a part of the sermon, part that actually wasn't in the notes.
I grant that my efforts may not have convinced everyone, though I will keep trying. But virtually all remotely-sound Christians will at least give a nod to the proviso that yes, yes, yes, the Bible is God's Word, and yes, it's some kind of sufficient, and no, no hemi-demi-semi-kindasorta revelation can displace it — well, not formally, anyway.
So agree with me on this. If you really believe what you say you really believe, this should be no problem. Here we go:
Agree heartily to believe in and use Scripture as befits what it claims about itself. Treat it like it is what you say you believe it is: God's actual, real-live, inerrant, personal, living and powerful Word. Approach it as you would actually approach such a treasure as you profess to affirm to have found in Scripture.
That is, pledge yourself exclusively to seek God and His will according to Scripture. Pray only for light to understand Scripture (cf. Psa. 119:18; 2 Tim. 4:7). Commit yourself only to regard what comes from Scripture as God's binding will for you. Set aside all the yeah-buts and evasions and distractions and special-pleadings and fourteenth-hand stories and traditions, for a time.
Set yourself to seeking and being in a church that emphatically teaches the Bible as if it were what it says it is, that devotes itself to the exposition and proclamation and practice of Scripture as God's inerrant word, without the endless distractions of entertainment and fads and dancing bears.
Devote yourself exclusively to studying Scripture, all sixty-six books. Set yourself to master every book, every chapter, every verse, every word. Seek perfect understanding of all of Scripture, and Scripture only, as containing what God really wants you to know. Memorize all of it.
Finally (and at the same time) commit yourself to practicing Scripture perfectly. All of it. Master it, and be mastered by it — exclusively. If it is not Bible or a valid straight-line application of the Bible, do not claim it as any level of special revelation from God.