The surah sets up the criteria for how sins are expiated under the Islamic framework:
Surah 47:2:
And those who believe and do righteous deeds and believe in what has been sent down upon Muhammad—and it is the truth from their Lord—He will remove from them their misdeeds and amend their condition.
In the previous scriptures that the Quran claims to confirm (Surah 25:35, Surah 46:10), God’s mechanism for erasing sin requires a substitutionary atonement and the shedding of innocent blood (the Passover lamb, the Levitical sacrifices, and ultimately Jesus Christ on the cross).
Surah 47:2 completely bypasses the entire covenantal, sacrificial theology of the Torah and Gospel by declaring that simply believing Muhammad's recitation wipes away sin. A polemicist can argue: "If the Quran confirms the Torah, why does it completely eliminate the absolute necessity of blood atonement established by God in the Torah?"