We do not posses any of the original manuscripts of the Bible, only copies. So can we know if what we have was really what the original texts said? This quote from George Henderson in The Wonderful Word sheds some light on the issue:
“On January 1, 1863, President Lincoln set his name and seal on the proclamation which set four million slaves free. The proclamation was written on four pages of ordinary foolscap in the president’s own handwriting. That document perished in the great Chicago Fire of 1871. Suppose some slave owner should seize a former slave of his, challenge him to produce Lincoln’s Proclamation as his charter of liberty, and say that if he did not produce the original, he would hold him still in slavery; what could the ex-slave do? He could not produce the original, for the original was destroyed by fire. Although he could not produce the original document, he could recover and produce the original text. How? By copies of the same in public documents; newspapers of the period; by translations of the text in French, German, and other languages; by quotations from the proclamation in speeches, periodicals and books. By comparing and combining all these, he could establish to satisfaction of a court of law the original message which gave him liberty.”
Even though we do not posses the original documents of the Bible, we can be confident that we posses the correct text because of the multiplicity of available manuscripts.