Where in the bible does it say the Torah is the only true Torah? I was asked this question by someone and I am shamed I was unable to give a response.

The answer, typically, is not so simple. In my opinion, it does not say anywhere that there could not be another Torah somewhere. Perhaps the Vedas are Torah? But we have no knowledge of that. All that we know is that what we call the Torah – and that includes the written and oral traditions – is the only Torah that the Jews received.

See Deut. Ch. 13; 18:15-20; 30:10-16; 31:9; 31:24-26

Now, on an esoteric level, the Kabbalah teaches that the Torah that we have is written in story format due to human history, but in fact represents a primordial Torah that existed before Creation, that God created the Torah first and used it as a blueprint for creating the world. How is that? How is it possible for a book to be a blueprint? Well, that’s Kabbalah, and I can’t explain it to you right now, but I can tell you this: If it is true, then it should be possible to look into the Torah and learn about all kinds of things in creation. Indeed, that is what our sages have said. The only person who was able to do this with great success was Solomon – he was a great naturalist, not from traveling the world, but from studying the Torah. And if you are a spiritually-sensitive person, the converse should also make sense to you: that it should be theoretically possible to look at nature and discover Torah. Only a master Kabbalist could do so, and in fact our tradition teaches that only Abraham was able to with any success. He was able to derive what we would call Jewish customs, such as eating matza at the full moon nearest the vernal equinox, from his study of nature.

That, as they say, is a long story made short.

Best,
Rabbi Seinfeld
http://rabbiseinfeld.blogspot.com