Quran 21:55 from Surah Al-Anbiyaa on Divine Marvels.
قَالُوٓاْ أَجِئۡتَنَا بِٱلۡحَقِّ أَمۡ أَنتَ مِنَ ٱللَّٰعِبِينَ
English translation: They said Have you come to us with the truth or you (are) of those who play
Transliteration: qalu aji'tana bil-haqi am anta mina al-la'ibina