Surah Al-Mulk (The All Authority), Verse 30

قُلْ اَرَءَیْتُمْ اِنْ اَصْبَحَ مَآؤُكُمْ غَوْرًا فَمَنْ یَّاْتِیْكُمْ بِمَآءٍ مَّعِیْنٍ 

Qul ara'aytum in asbaha maaa'ukum ghawran famai ya'teekum bimaaa'im ma'een

“Say: "See ye?- If your stream be some morning lost (in the underground earth), who then can supply you with clear-flowing water?"”

Quran 67:30 (Yusuf Ali Translation)