Surah 7:187
"They ask you about the Hour: ‘When is its arrival?’ Say: ‘Knowledge of it is only with my Lord. No (one) will reveal it at its (appointed) time but He. It is heavy in the heavens and the earth, (but) it will only come upon you unexpectedly.’ They ask you as if you are well informed about it. Say: ‘Knowledge of it is only with God, but most of the people do not know (it).’"
Verses about “the Hour” usually seem to refer to the Day of Resurrection, but in this case “they” may be asking the messenger about the arrival of judgment on “disbelievers” in this world on the pattern of the punishment narratives in this sūra. References to the “Day” or the “Hour” become especially frequent in Sūras 11–47.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam