Is it forbidden to discard the Torah and the Gospel, or is it obligatory to preserve them, by analogy with the impermissibility of discarding a copy of the Qur’an?

One must believe in all of God's messengers and His revealed books. It is not permissible to disrespect the Torah and the Gospel, for they still contain some truth, and words of God, and His names and attributes. It is not permissible for a Muslim to possess these books unless he is a person of knowledge. One disposes of them by burning them, not by desecrating them.