All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Every single word in the holy Quran is from the speech of Allaah the Exalted and this includes the speech of others, like when Allaah The Almighty Says (what means):
In fact, this is a reported, not quoted, speech. As-Suyooti reported on the authority of Ibn Jinni his comment on the verse where Allaah the Almighty Says (what means): {They said, -“O Moses, either you throw or we will be the first to throw…”} [Quran 20:65]. He (Ibn Jinni) mentioned that all the speech of non-Arabs which is mentioned in the Quran is in the form of reported speech. In other words, what is mentioned in the Quran is the meaning of their words not their exact words. This way, when Allaah the Exalted Says (what means): {They said, -“Indeed, these are two magicians who want to drive you out of your land with their magic and do away with your most exemplary way.} [Quran 20:63] it is without doubt that such rhetoric was not part of the language of non-Arabs.
Allaah Knows best.