Is it permissible for a person afflicted with urinary incontinence, who combines two prayers, to perform ablution for Dhuhr prayer at its very end before the time for Asr prayer begins, in order to be able to pray Asr in congregation? And is he obligated to maintain the sequence between the two prayers when delaying them (jam‘ al-ta’khir), such that he prays Dhuhr first then Asr, or is it permissible for him to pray Asr with the congregation first, and then pray Dhuhr afterward?

The person afflicted with سلس ( سلس البول / سلس الريح / سلس المذي ) performs ablution after the time for the prayer being combined has begun. So, for an early combination (جمع التقديم), he performs ablution at the time of the first prayer, and for a delayed combination (جمع التأخير), he performs ablution at the time of the second prayer. It is permissible to combine two prayers with a single ablution, based on the hadith: "Perform ablution for the time of every prayer," and because it is an ablution that permits both supererogatory and obligatory prayers. Many scholars stipulate that for the validity of a delayed combination, the two prayers must be performed in order.