The Quran devotes 22-25% of its text to the stories of the prophets, which it claims in Surah 12:111 is a "confirmation of the previous scriptures and a detailed explanation of all things."
However, when comparing the 98 verses of the story of Joseph in the Quran to the Torah's version, there are many irreconcilable differences.
Muslims argue that because the Quran is correcting the errors introduced by human hands into the previous scriptures, it does not need to align with the Bible.
They cite Surah 5:15 alongside Islamic commentaries (Tafsir) to argue that the Quran's role is to expose what the People of the Book concealed and to correct biblical corruption.
The story of Joseph in the Quran (AD 632) comes approximately 830 years after the earliest Genesis manuscripts about Joseph found in the Dead Sea Scrolls (250-150 BC). It bears little resemblance to the Quranic account.
The Textual Reality of Surah 5:15:
Islam has to rely on Tafsir (commentaries) because the actual text of Surah 5:15 only accuses Jews and Christians of concealing parts of their book, NOT physically altering the manuscripts.
The Internal Quranic Contradiction:
If the Bible was already corrupted by the 7th century, the rest of Surah 5 becomes incoherent.
Allah would not command people to judge by textually corrupted books.
When a seeker in the 7th century (or today) obeys Surah 10:94 and compares the 98 verses of Surah 12 to the text of Genesis—corroborated by the Dead Sea Scrolls, the Septuagint, and ancient historians like Josephus—they do not find a "confirmation."
Instead, they find hundreds of irreconcilable differences in plot, characterization, and dialogue. This creates an inescapable contradiction for the authority of the Quran.
If the previous scriptures are true, the Quran is false because it contradicts them. If the previous scriptures were already completely corrupted and unreliable by the 7th century, then Allah’s command to use them as an external benchmark of verification makes no logical sense.
Therefore, the Christian rejects the Quran as authoritative because it fails its own standard of textual validation.