Al-Kahf · 18:19

19. Just as I did to them the wondrous acts that I have mentioned, I awakened them after a long period of time and they began to ask one another about the period that they had spent asleep. One of them responded: I remained asleep for one day or part of one day. One of them, to whom it was not clear how long they had spent asleep, responded: Your Lord knows best about the period you had remained asleep, so entrust the knowledge of that to Him and get busy with what concerns you. Send one of you with these silver coins to the city we know and let him see which of the inhabitants of that city are most pure in their food and earnings. He should proceed with caution when entering and leaving and when dealing. He must also be tactful and not let anyone find out where you are, because that will result in great harm.