[That was] when they disputed among themselves about their affair and [some] said, "Construct over them a building. Their Lord knows best about them." Those who prevailed in their matter said, "We will surely take for them a masjid." They will say there were three, the fourth of them being their dog; and they will say there were five, the sixth of them being their dog—guessing at the unseen; and they will say there were seven, and the eighth of them was their dog. Say, "My Lord is most knowing of their number. None knows them except a few. So do not argue about them except with an obvious argument and do not inquire about them among [the speculators] from anyone."} (Al-Kahf: 19-22).

As for His saying: {Construct over them a building}, it is an indication to demonstrate that it is not permissible to reveal their affair.

And His saying: {Those who prevailed in their matter said, "We will surely take for them a masjid."} Indeed, the "masjid" here contains more than the wall which al-Khidr (peace be upon him) built over the treasure. This is because the masjid indicates both worship and concealment (al-tastur) simultaneously.

And His saying: {So do not argue about them except with an obvious argument.} This is a total and explicit declaration regarding the concealment of the Inward (al-Bāṭin).

And His saying: {And do not inquire about them among [the speculators] from anyone} means: do not seek a formal legal opinion