What is the interpretation of the verse: "And you would have seen the sun, when it rose, inclining away from their cave to the right, and when it set, passing away from them to the left, while they were in a spacious opening therefrom. That is of the signs of Allah. He whom Allah guides is the [rightly] guided, but he whom He sends astray - never will you find for him a protecting guide" (Al-Kahf/17)?

The gist of the answer:

Allah protected the People of the Cave from the sun's heat by making their cave slanted away from it, both morning and evening, so its rays did not reach them. They were in "a wide opening within it," meaning a spacious place inside the cave, so that air would reach them and the confinement of the place would be removed, especially given the long duration of their stay there. This is among Allah's signs, demonstrating His power and mercy towards them, His answer to their supplication, and His guidance to them. For this reason, it is said: "Whom Allah guides is the [rightly] guided," for there is no guidance except from Him, and "whom He sends astray – never will you find for him a protecting guide," because he will not find anyone to befriend him or guide him to goodness and success once Allah has decreed his misguidance.