And just like that, We made the people know about them so that they might know that the Promise of Lord Allah is True and that there is no doubt about the Last Hour; when they disputed among themselves about their affair and said: "Construct over them a structure. Their Lord is most knowing about them". Then those who prevailed in the matter said: "We will surely construct over them a Masjid."
The aimless and heedless people of that period did not believe in the Resurrection. So Lord made them know about these youths to show that Lord’s Promise is True and the Last Hour will happen. The Promise of Lord upon the believers is that He will save them beyond cause and reason as explained in verse 10: 103. And the Promise of Lord upon mankind is that He will resurrect them all for the Day of Judgment.
A few moderate persons among the people advised to separate them building a wall. But the chiefs and majority planned to build a Masjid upon them. Just like that, today the Arabic Quran reading Fujjar by hiding and rejecting Adhikr are giving importance in building huge Masjids all over the world. Thus, they are testifying the teaching of Lord through His Messenger that “Their Masjids will be huge concrete buildings, but they will be strayed from the Guidance –Adhikr” as explained in verses 2: 114-115 and 9: 107-110. See explanation 8: 35; 9: 17-18 and 67-68.