Prayer: The Time of the Nafilah of Asr
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 756
The nafilah of asr is performed before the asr prayer, and its time continues until the time it is possible to perform it before performing the asr prayer. However, if one delays performing the nafilah of ʿaṣr until the time that the shadow of an indicator becomes four-sevenths the length of the indicator, it is better to perform the asr prayer before the nafilah prayer, except in the case mentioned in the previous ruling.