It does not invalidate the prayer merely due to exposure during the prayer, even if one's private parts are exposed while praying, and then one immediately covers themselves; their prayer is not invalidated. Rather, it is invalidated by the passage of a specified time, which is if they perform a pillar of the prayer in reality while exposed, according to Muhammad (may God have mercy on him). According to Abu Yusuf (may God have mercy on him), it is if a time passes during which a pillar of the prayer can be performed – that is, the duration of three tasbihs. This applies if the private parts are exposed during the prayer. However, if the exposure coincides with the beginning of the prayer, it prevents the prayer from being valid if the exposure is a quarter of the limb or more; because covering the private parts is a condition for the validity of commencing the prayer, and without it, the commencement is not valid. See: Maraqi al-Falah, pp. 210-211; Al-Wiqayah and its explanation by Sadr al-Shari'ah, 1: 143; Radd al-Muhtar, 1: 408; Bada'i al-Sana'i, 1: 117; and Al-Hadiyyah al-Alaiyyah, p. 72.