Previous reasons given are compelling, but this one is the most persuasive of all: The Son of God Himself believed and taught the Bible's complete inspiration and reliability. The One who is considered by even non-Christians as the wisest and most saintly person who ever lived taught the infallibility of the Bible, saying such things as, "It is written... Search the Scriptures... Have you read... Scripture cannot be broken."
He spoke of the total accuracy of even the "jot" and "tittle," the smallest characters of the Hebrew alphabet.
He spoke confidently about past events and people, such as Noah and the ark, Jonah and the whale, Abraham and Moses. The holy Son of God could not deceive, nor was He ignorant, having all knowledge.
Even after His resurrection, in His glorified body, Christ taught the infallibility of the Scriptures. On one occasion, He rebuked His disciples for being "slow of heart to believe all that the prophets have spoken." (He said all, not some!)
Of course, in Jesus' day, there was no New Testament, which was written later under His direction. But He placed His stamp of authority on it by anticipation when He told the disciples,
But the Counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you (John 14:26).