This verse assigns to the Torah the highest possible status in Islamic theology: the Furqan (The Criterion).
Surah 2:53:
"And when We gave unto Moses the Scripture and the criterion, that ye might be led aright."
In Islamic theology, the Quran is often called Al-Furqan (The Criterion). However, Surah 2:53 explicitly grants this identical title to the Torah given to Moses.
If the Torah is the "Criterion," it is the standard against which all subsequent claims must be measured. A criterion does not change; it is the "ruler" used to measure everything else.
If the Quran contradicts the Torah (as shown in previous discussions regarding the sacrifice of Isaac or the nature of atonement), then the Quran fails the test of the "Criterion" that God gave to Moses. You cannot have two "Criteria" that contradict each other.
The verse states the Torah was given so that the people "might be led aright."
If a book is given by God for the specific purpose of guiding people "aright," it implies that the book is clear, protected, and effective.
If the Torah became "corrupted" to the point where it leads people into shirk (believing Jesus is the Son of God) or false history, then God's "Criterion" failed its primary purpose. Why would God give a "Criterion" only to allow it to become a source of mass deception?
This verse is directed at the 7th-century Jews of Medina, reminding them of what Moses was given.
The reminder only works if the Jews still have access to that "Criterion." If the book was gone or unrecognizable, the reminder would be meaningless.
By pointing back to the Torah as the Furqan, the Quran validates the 7th-century Jewish scriptures. Since we have those same scriptures today (the Masoretic text), the Quran has effectively endorsed the very book that excludes Muhammad's prophetic claims.
The Quran calls the Torah the Furqan—the Criterion. A criterion is the fixed standard used to judge everything else.
If I use the Furqan given to Moses to judge the Quran, I find that the Quran fails. It changes the laws, it changes the history, and it changes the way of salvation.
If the Torah is the Criterion, as 2:53 says, then the Quran is measured and found wanting. If the Torah is not the Criterion, then 2:53 is false.