The Koran presents Judaism as a corrupted version of the true Abrahamic religion.

Evidence

Yet there were conflicts with Jews in Medina, and it is in this context that the Medinese Sûras assert that Islam is the true uncorrupted form of the religion of Abraham, that Judaism has been sullied by the worship of the golden calf in Sinai, by failure to abide by God’s law, and by willfully “altering words from their proper meanings.” The Koran echoes the Christian polemical attack on “blindness” of the Jews: “Those to whom the burden of the Torah was entrusted and yet refused to bear it are like a donkey laden with books. Wretched is the example of those who deny God’s revelation.” Jews (and Christians), it seems, misinterpret their scripture so as to deny the antiquity of Islam and the prophethood of Muhammad. Later Muslim authors will accuse Jews (and Christians) of falsification of scripture (tahrîf): deliberately expunging prophecies relating to Muhammad from the Torah and Gospel. Judaism in its present form is a corrupted, imperfect version of the true religion revealed to Abraham and Moses. It is to be tolerated but never to be granted equal footing with Islam. — John V. Tolan, Saracens, 248

Categorization

• DEFINE: Introduces tahrîf, the doctrine of scriptural falsification, and the specific accusation that Jews and Christians expunged prophecies of Muhammad.
• XREF: Connects to the reader’s broader interest — the theological mechanics of how ex-monotheistic rivals get reframed as corrupted versions, similar to early Christian polemics against Jews.