ثُمَّ لَتُسْأَلُنَّ يَوْمَئِذٍ عَنِ النَّعِيمِ
Then on that Day you will surely be questioned about blessings. (التكاثر: 8)
La-tusʾalunna is a passive verb reinforced by an emphatic lām and heavy nūn. The grammatical focus is placed on the audience as those who will answer, rather than on explicitly naming the questioner. Yawmaʾidhin locates the questioning on that Day; ʿani al-naʿīm identifies its subject.
A passive construction does not mean the questioner is unknowable in reality. Grammatical non-expression and lack of knowledge are different. Here the form makes the listeners confront their own accountability.