Is it obligatory for someone afflicted with incontinence to perform ablution (Wudu') for Dhuhr prayer if he had performed ablution before the time for Dhuhr and his ablution was not invalidated by the exit of the prayer time?

A person with an excuse (ma'dhur) performs ablution for each prayer time when something exits [his body]. It is not permissible to perform ablution for an obligatory prayer before its time enters. The purification of the person with an excuse becomes void with the entry and exit of the prayer time, such as a woman with prolonged vaginal bleeding (mustahadah) and a person suffering from urinary incontinence (sals al-bawl), based on the Prophet's (peace and blessings be upon him) saying: "And perform ablution for every prayer."