John Gill Commentary Joshua 8:28

"So Joshua burnt Ai, and made it a heap for ever, even a desolation, unto this day." — Joshua 8:28 (ASV)

And Joshua burnt Ai
The whole city, fire being only set before to a few houses, to make a smoke as a signal; he did with it as he had done with Jericho, for so he was ordered, (Joshua 8:2);

and made it an heap for ever ;
that is, for a long time, for it appears to have been rebuilt, and to have been inhabited by the Jews, after their return from their Babylonish captivity, (Nehemiah 11:31);

[even] a desolation unto this day ;
to the time of the writing of this book; and by what has been just observed, it appears that Ezra could not be the writer of it, since this city was inhabited in his time.