Surah Al-Anbiya' (The Prophets), Verse 38

وَیَقُوْلُوْنَ مَتٰی هٰذَا الْوَعْدُ اِنْ كُنْتُمْ صٰدِقِیْنَ ۟

Wa yaqooloona mataa haazal wa'du in kuntum saadiqeen

“They say: "When will this promise come to pass, if ye are telling the truth?"”

Quran 21:38 (Yusuf Ali Translation)