Quran 18:20 — The Cave (Al-Kahf)

"If they discover you, they will stone you, or force you to revert to their religion, then you can never succeed."

[18:19] When we resurrected them, they asked each other, "How long have you been here?" "We have been here one day or part of the day," they answered. "Your Lord knows best how long we stayed here, so let us send one of us with this money to the city. Let him fetch the cleanest food, and buy some for us. Let him keep a low profile, and attract no attention.

[18:21] We caused them to be discovered, to let everyone know that GOD's promise is true, and to remove all doubt concerning the end of the world.* The people then disputed among themselves regarding them. Some said, "Let us build a building around them." Their Lord is the best knower about them. Those who prevailed said, "We will build a place of worship around them."