Prayer: Doubting the Performance of Zuhr During Asr
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 745
If a person doubts during the ʿaṣr prayer whether he has performed the ẓuhr prayer or not, he must complete the prayer with the intention of the ʿaṣr prayer and after that perform the ẓuhr prayer. However, if the time is so little that after completing the ʿaṣr prayer, the time for prayers ends and there is not enough time remaining to perform even one rakʿah, it is not necessary to make up the ẓuhr prayer.