Prayer: The Time of the Nafilah of Subh
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 759
The nāfilah of the ṣubḥ prayer is performed before the ṣubḥ prayer. Its time commences after the time it takes to perform the night prayer (ṣalāt al-layl) at its earliest time, and continues until there is still time to perform it before the ṣubḥ prayer. However, if one delays performing the nāfilah of ṣubḥ until the redness of the eastern sky becomes visible, it is better that he first perform the ṣubḥ prayer.