What we have today in the Bible is exactly what our Heavenly Father wanted in there. Nothing more and nothing less. It is he that preserves his word forever, not man.
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And who inform you?
Who informs me? Well...how about belief in an all powerful, all knowing God who is able to preserve his word just like he said he would.
Isaiah 40:8 (King James Version)
The grass withereth, the flower fadeth: but the word of our God shall stand for ever.
Matthew 24:35 (King James Version)
Heaven and earth shall pass away, but my words shall not pass away.