What is the ruling on wiping over the hijab to renew wudu when it is difficult to remove, and is it permissible to do so if waiting would cause the prayer time to expire?

If it is possible for a woman to wipe part of her head and then complete the wiping over her head covering (khimar), that is preferable. However, if this is difficult for her, the correct view is the permissibility of wiping over the khimar, just as a man wipes over his turban, regardless of whether the khimar is difficult to remove or not. This is the madhhab of some scholars, such as Ibn Hazm and Ibn Taymiyyah, and it has been narrated from Umm Salama. Sheikh Ibn Uthaymeen holds the view that wiping over the khimar is permissible when there is difficulty. Ablution (wudu') is not required if purity has not been nullified.