Surah Yasin, ayah 48

36:48

وَيَقُولُونَ مَتَىٰ هَٰذَا ٱلۡوَعۡدُ إِن كُنتُمۡ صَٰدِقِينَ ٤٨

Wayaqūlūna matā hādhal-wa'du in kuntum sādiqīn

And they say, "When is this promise, if you should be truthful?"