Is it necessary to renew the intention for combining the daily Dhuhr and Asr prayers, and the Maghrib and Isha prayers, at the time of the second prayer for those with excuses, such as incontinence, or is it sufficient for them to intend it once, given that the prayer time for them extends to the second obligatory prayer?

For the validity of delaying prayers (jam' al-ta'khir), the intention must be made at the time of the first prayer. This intention distinguishes between a permissible and an impermissible delay. Thus, whoever delays a prayer without the intention of combining them until its time expires, it becomes a qada' (missed prayer) and they incur sin. As for past prayers that were performed without the intention of combining due to ignorance, it is hoped that there is no sin upon them, and they are considered sufficient and fulfilling of the obligation, but they are qada' (missed) and not ada' (on-time performance). For future prayers, the intention to combine must be made at the time of the first prayer.