Prayer: Time Scarcity and Recommended Acts
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 734
If the time remaining for prayers is so little that by performing some of the recommended (mustaḥabb) acts of the prayer a part of the prayer would have to be performed after its prescribed time, one must not perform those recommended acts. For example, if by performing qunūt[1] a part of the prayer would have to be performed after its prescribed time, he must not perform qunūt. Furthermore, if he does perform that recommended act, his prayer is valid only if at least one rakʿah of it was performed within the prescribed time.
-Ayatullah Sistani, Practical Laws of Islam, Prayer (Salah)
1
This is the act of supplicating in prayers with the hands placed in front of the face.