Is it permissible for the excused person who performed ablution for the Dhuhr prayer to pray the Asr prayer with the same ablution if it was not nullified, or must he renew his ablution?

The Asr prayer is not valid if one performs ablution (wudu') before its time for someone afflicted by a perpetual ritual impurity (hadath da'im). This is due to the long interval between purification and prayer, and the occurrence of the impurity after purification. A person afflicted by perpetual impurity must perform ablution for each prayer after its time has begun. However, if the impurity ceases before ablution and does not return, then it is permissible for the one who performed ablution to pray with that ablution.