You need something external to the Bible to prove it. Why do you believe in the Bible? Just because it says so? You people make it so easy for athiests to lampoon Christianity.
Faithful is He that calleth you for He will also do it. Many are called but few are chosen. And stubborn rejection of the Truth The Word declares shows us all why so few are chosen, for so few will let Him do the saving, the birthing from above, because they are always demanding more proof than spiritual awakening. And in such demands these reject the actual Grace of God's Spirit awakening them to The Truth The Word of God declares.
The witnesses to the events of the Bible are what prove it.
That you don't agree with it I cannot help.