وَمَآ أَهْلَكْنَا مِن قَرْيَةٍ إِلَّا وَلَهَا كِتَابٌ مَّعْلُومٌ
Wa maaa ahlaknaa min qaryatin illaa wa lahaa kitaabum ma'loom
Never have We destroyed a community that did not have a set time;
Never have we destroyed a town except that it had a known decree.
The word for what each town had is kitāb, a writing, the same noun this surah uses three verses earlier for the Book being recited. The unit being reckoned with is the qarya, a settlement, so the accounting is of a whole community rather than of the people inside it one by one. Ma'lūm, known, states that the term is known to God while saying nothing about who else knows it.