God said so. He promised the prophets of old that He would preserve His word for all generations. Jesus told the apostles that the Holy Spirit would bring to their remembrance all that He said and that we were promised that indwelling of the Holy Spirit as a guide and teacher. The oracles of God in the Old Testament were entrusted to the Jews who preserve them to this day. The words of the New Testament were entrusted to the apostles and whose writings have been preserved through multiple means for us today. To God and God alone be the glory and praise.
LOL, so you believe the bible is God’s word because the bible says so? And the reason you’re not Muslim or Mormon is...what exactly?
Got anything besides circular “reasoning”?