Peter says that the word is more sure than the voice of God.
And don't forget:
Psalms 138:2
I will worship toward thy holy temple, and praise thy name for thy lovingkindness and for thy truth: for thou hast magnified thy word above all thy name.
Does it say "written" word? No, the voice of God does not come to man by letters on a page - but through the LIPS of prophets and messengers. Don't forget that. The Bible is full of such men...
Regards