Answer
(Fatwa: 855/855=J)
It is haram whether in salah or in normal condition to wear the pants, trousers etc below ankles. There have been narrated a couple of severe punishments for the same. However, wearing pants etc below ankles in salah is worse and it makes salah makrooh-e-tahreemi (undesirable to haram extent). Therefore, you should wear it above ankles so that you are sinful neither in salah nor out of salah.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband