وَيَقولُ الَّذينَ كَفَروا لَستَ مُرسَلًا ۚ قُل كَفىٰ بِاللَّهِ شَهيدًا بَيني وَبَينَكُم وَمَن عِندَهُ عِلمُ الكِتابِ

And those who have disbelieved say, "You are not a messenger." Say, [O Muhammad], "Sufficient is Allah as Witness between me and you, and [the witness of] whoever has knowledge of the Scripture."