Surah Ar-Ra'd (The Thunder), Verse 43

وَیَقُوْلُ الَّذِیْنَ كَفَرُوْا لَسْتَ مُرْسَلًا قُلْ كَفٰی بِاللّٰهِ شَهِیْدًا بَیْنِیْ وَبَیْنَكُمْ وَمَنْ عِنْدَهٗ عِلْمُ الْكِتٰبِ 

Wa yaqoolul lazeena kafaroo lasta mursalaa; qul kafaa billaahi shaheedam bainee wa bainakum wa man 'indahoo 'ilmul Kitaab

“The Unbelievers say: "No messenger art thou." Say: "Enough for a witness between me and you is Allah, and such as have knowledge of the Book."”

Quran 13:43 (Yusuf Ali Translation)