They claim the prophet forged it; if that is the case, then his APA citation must have been impeccable.
In reality, Allah declares that the Qur'an came to confirm that which was in the previous scriptures.
The most sublime example occurs with regards to a conversation regarding the People of Lot.

In the Old Testament, Abraham pleads with Allah through his angels regarding the fate of the people of Soddom
The exchange in Genesi 18 goes
"And Abraham approached and said, "Will You even destroy the righteous with the wicked?

Perhaps there are fifty righteous men in the midst of the city; will You even destroy and not forgive the place for the sake of the fifty righteous men who are in its midst?

Far be it from You to do a thing such as this, to put to death the righteous with the wicked so that the righteous should be like the wicked. Far be it from You! Will the Judge of the entire earth not perform justice?"

And the Lord said, "If I find in Sodom fifty righteous men within the city, I will forgive the entire place for their sake.

And Abraham answered and said, "Behold now I have commenced to speak to the Lord, although I am dust and ashes.


Perhaps the fifty righteous men will be missing five. Will You destroy the entire city because of five?" And He said, "I will not destroy if I find there forty-five."

And he continued further to speak to Him, and he said, "Perhaps forty will be found there." And He said, "I will not do it for the sake of the forty."

And he said, "Please, let the Lord's wrath not be kindled, and I will speak. Perhaps thirty will be found there." And He said, "I will not do it if I find thirty there."

And he said, "Behold now I have desired to speak to the Lord, perhaps twenty will be found there." And He said, "I will not destroy for the sake of the twenty."

And he said, "Please, let the Lord's wrath not be kindled, and I will speak yet this time, perhaps ten will be found there." And He said, "I will not destroy for the sake of the ten.""




Allah reminds us of this in the Qur'an regarding his mercy, regarding this very conversation, and regarding the depravity of the city saying that
"So We brought out whoever was in the cities of the believers.
And We found not within them other than a [single] house of Muslims" (51:35-36)

For the sake of 10, the Lord would have spared the twin cities. But he comes back in the Qur'an to inform us that there was not even that number within the city.