If the Quran is the Word of God, then why doesn’t it contain earlier portions of God’s Word?
Previous prophets built upon what God had revealed to earlier generations. Proof of this is that can be seen that the Bible, the Word of God, consists of many books by earlier prophets. Jews and Christians both read in their Bibles what Moses wrote. Muslims don’t. Muslims are only left with what Muhammad said about Moses.
Christians and Jews share the Hebrew Scriptures.
Islam is unlike Christianity and Judaism because it has omitted earlier revelation of the Word of God from the Quran. This means Muhammad was unlike previous prophets. Muhammad was unlike Jesus Who taught that he did not come to abolish the Law or the Prophets (Matthew 5:17-18).
Here is an example of Muslim omission given by the Grand Mufti of Saudi Arabia who was asked,
Answer: Almighty God said: “These are the verses of the perspicuous book. We have sent it down as an Arabic Qur’an, in order that ye may learn wisdom. We do relate unto thee the most beautiful of stories, in that we reveal to thee this portion of the Qur’an. Before this, thou too was among those who knew it not” [Qur’an 12:1-3]. He (also) said: “Such are some of the stories of the unseen, which we have revealed unto thee: before this, neither thou nor thy people knew them” [Qur’an 11:49]. The stories in the Qur’an are more valuable than any others–we don’t need the Torah, or Gospels, or any other book. We believe that truth was sent down to the prophets, but God has enriched us more with the Qur’an and its stories than with all the (other) books. This Qur’an is the true account: “This is the true account; there is no god but God” [Qur’an 3:62]. We should take the stories and understanding from this great book. Regarding the previous books, their role has ended, and there is no longer any place for them. Almighty God has gathered all of their meaning into the Qur’an. The Qur’an has become dominant over them, and a substitute for all of them. The Qur’an with its stories and knowledge are sufficient for us. (Translating Jihad)
According to this explanation, the purposes of the Jewish and Christian Scriptures have ended. The Quran is more valuable. The Quran is the “true account” which implies his belief that the Jewish and Christian Scriptures have been corrupted.
If Muslims took the time to love God with all their mind, they would learn that the Quran is not the “true account” (Matthew 22:36-37). This is most clearly seen in the Quran’s rejection rejection of Jesus’ death on the cross (Quran 4:157–158).