When is the ablution of those with excuses, who combine prayers nominally with a single purification, invalidated? Is it by the exit of the time for the second obligatory prayer, or immediately upon the completion of the second prayer? And is the purification invalidated by a separation between the two obligatory prayers due to supererogatory prayers or going to the mosque, if something (from the سلس - continuous discharge) is emitted by the person concerned?

The excused, such as a woman with istihada (non-menstrual vaginal bleeding) and a person with sals (urinary incontinence), are permitted to combine every two prayers of combination with a single purification (taharah) during the time of one of them. They can perform these prayers and as many supererogatory (nawafil) and missed (fai’tat) prayers as they wish with that single purification, according to the preponderant view among scholars, which is the madhhab of the Hanafis and Hanbalis. The Malikis hold that sals which is constant for half the time or more does not invalidate wudu’ (ablution). Thus, such a person may pray the five obligatory prayers with their wudu’ as long as their wudu’ is not invalidated by something other than the sals event. This applies if they are unable to stop it. If they are able to stop it, then it invalidates wudu’ absolutely. Most jurists, however, believe that wudu’ becomes invalid upon the entry of the time for the next prayer, and some say it becomes invalid upon the expiry of the time for the prayer for which wudu’ was performed. The correct view according to the Hanafis is that wudu’ becomes invalid upon the expiry of the time for the obligatory prayer due to the pre-existing hadath (event that invalidates wudu’). The Shafi'is hold that a person with sals must perform wudu’ for each prayer, even if combined with another. They mentioned six conditions: tightening (the bandage), binding (the area), performing wudu’ for each obligatory prayer after the time for it has entered, renewing the bandage for each obligatory prayer, intending to permit the prayer (niyyat al-istibahah), and immediately proceeding to prayer. With this wudu’, they may only perform as many supererogatory prayers as they wish. The Hanbalis are like the Shafi'is in all of this, except for the issue of wudu’ for each obligatory prayer. They hold that a person with constant hadath performs wudu’ for each prayer time and may pray as many obligatory and supererogatory prayers as they wish with it, as long as the time does not expire.