Quran 36:48 from Surah Yaseen on Divine Marvels.
وَيَقُولُونَ مَتَىٰ هَٰذَا ٱلۡوَعۡدُ إِن كُنتُمۡ صَٰدِقِينَ
English translation: And they say When (is) this promise if you are truthful
Transliteration: wayaquluna mata hadha al-wa'du in kuntum sadiqina