The Bible is the inspired and only infallible and authoritative written Word of God.

All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness  (2 Timothy 3:16)

For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard of us, ye received it not as the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.  (1 Thessalonians 2:13)

For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.  (2 Peter 1:21)