Quran 10:48 from Surah Yunus on Divine Marvels.
وَيَقُولُونَ مَتَىٰ هَٰذَا ٱلۡوَعۡدُ إِن كُنتُمۡ صَٰدِقِينَ
English translation: And they say When (will) this the promise (be fulfilled) if you are truthful
Transliteration: wayaquluna mata hadha al-wa'du in kuntum sadiqina