There is a difference of opinion among the schools of thought regarding the time for Witr prayer, which can be divided into two opinions:
The first opinion is held by the Ḥanafiy and Mālikiy schools of thought, who believe that the time for Witr prayer begins after the disappearance of the red twilight, which is the original time for the Isha prayer. The Ḥanafi school of thought does not allow combining the prayers except in specific places: ʽArafāt and Muzdalifah, as well as what is called “al-Jamʽ aṣ-Ṣūriy (descriptive combination of prayer)” which is delaying the earlier prayer to its last time (Maghrib) and advancing the later prayer to its earliest time (Isha). Therefore, according to them, Witr prayer cannot be performed before the actual time for Isha prayer. The Mālikiy school of thought, although they allow combining the prayers in Maghrib and Isha, they do not pray Witr before the disappearance of the red twilight, which is the actual time for Isha prayer, as there is no difficulty or necessity for doing so.
The second opinion is held by the Shāfiʽiy and Ḥanbaliy schools of thought, who allow performing Witr prayer after the prayer that is performed before its time with the excuse of applying combining. Therefore, according to them, Witr prayer follows the Isha prayer, whether it was performed earlier or later. After all, Allāh knows best.
Fatwa by Dr. Khālid Naṣr