وَأَنَّا لَمَسْنَا ٱلسَّمَآءَ فَوَجَدْنَـٰهَا مُلِئَتْ حَرَسًا شَدِيدًا وَشُهُبًا
Wa annaa lamasnas sa maaa'a fa wajadnaahaa muli'at harasan shadeedanw wa shuhubaa
A my dotknęliśmy nieba i znaleźliśmy je wypełnione strażami i płomieniami ognia.
And we reached toward the heaven and found it filled with mighty guards and blazing flames.
Testimony here is first-hand: the jinn are reporting what they met when they went up, and the verb lamasnā is the one for feeling your way toward something by hand. Verse 9 dates the change with the word now, so what they describe is a night watch that has just been reinforced. Whether the barring began then or was only tightened has long been argued, since 15:17 already describes the sky guarded.