Let me ask you, how do you determine something to be true?
That the Jews--perhaps as many as three thousand people--stood at Sinai and heard the Voice of G-d is known because they were there. How often do I have to say that? They . . . were . . . there. They never forgot. They passed it on to all their descendants in an unbroken line. Unlike so many chrstians, who believe in G-d because the Bible tells them to, they believe in the Bible because G-d told them to. This is the only claim of national revelation in history. It is also the only self-vindicating religious claim in history. The story of Sinai could not have been created and injected later. It actually happened. And because it happened, we know the Torah is from Heaven. This means the Torah sits in judgment on all later claims of revelation--every one of them.
Have you read this article yet? It explains things quite nicely.
The amazing thing is that as a chrstian you actually accept the Revelation at Sinai. But you don't accept it because your ancestors were there and the experience has been handed down to you in an unbroken chain. You accept it because the event is described in your bible (you accept J*sus for the same reason--he is in your bible). Yet you refuse to recognize that this revelation which you yourself accept simply does not allow for any new religions or religious beliefs other than those received at Sinai. If you could cast off your blinders and read the Torah without your a priori belief in chrstianity you would see that the Torah warns over and over and over and over again to never deviate from it ever. But you can't accept this because you assume from the get go that the "new testament" is part of the "very same bible."
As a matter of fact, all verses that threaten the exile of the Jewish People and the destruction of the Temple in the Torah make it clear that this is a punishment for deviating from the Torah. Chrstianity quite dishonestly denies this plain fact and instead insists the punishment is not for switching to the new religion when the old one had "expired!"
Would it do any good in the world to explain to you that I'm not Jewish? That I used to be chrstian? That I used to believe exactly as you do? All you have to do is drop your a priori assumptions.
I suppose you also won't believe me when I tell you (and once again, I used to believe exactly as you do) that your version of "chrstianity" is not the real thing. Protestantism (or "bible chrstianity" if you prefer) did not exist until the sixteenth century. The actual historical chrstian religion is the one practiced by Catholics, Eastern Orthodox, Oriental Orthodox, and Nestorians. There is no such thing as an ancient "bible church" anywhere in the world. All the ancient churches (some of which were outside Rome altogether and which Constantine never had anything to do with) have priests, confession, the "holy sacrifice," pray to Mary and the saints, etc. Every . . . single . . . one. Go to YouTube and watch some of their services. Do you think Constantine somehow caused an ancient "Baptist" church in Ethiopia to become the Ethiopian Orthodox Tewahedo Church? Constantine never had anything to do with Ethiopia, or Armenia, or Persia, or India. Go ahead . . . watch a worship service of any of those churches. Why be a chrstian if the "chrstianity" you practice isn't even authentic?
Oh and, btw, every one of those ancient churches reject the Protestant concept of justification, once-saved-always-saved, and that salvation consists entirely of the vicarious eternal damnation of J*sus in our place. In fact they spend their entire lifetimes obeying commandments and praying and hoping that they don't go to hell when they die, because they can never be sure. May I ask why in the world a new religion of commandments was needed when the original Biblical religion already had the same thing? Historical chrstianity is an imitation of Torah Judaism. Protestantism is logical enough to see this and therefore must defend the myth that the "original chrstianity" was identical to today's "bible chrstianity" and that Constantine corrupted it.
I had to face every one of these facts. You may choose not to, but they are still the facts. I'm afraid that outranks personal experience.