Thus We let them be discovered so that they would know that God's promise is true and that there is no doubt regarding the moment. They argued amongst themselves regarding them, so they said, "Erect a monument for them!" Their Lord is fully aware of them. Those who managed to win the argument said, "We will construct a temple over them."
Translation endnotes
[18:9-27] These 19 verses contain numerous key words that strongly imply that the story of the cave have double meaning like the verses in chapter 74, and the second meaning is about a prophetic event. I have already observed examples of a hidden mathematical design, and God the most Wise will unveil it when the right time comes. When the secrets contained in the cave is revealed by divine permission, it will prove once again the truth in the assertion at 18:27. [18:21] The numbers related to this event shed light on the question regarding the end of the world. See 18:25.