Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- It is highly recommended to perform witr, as it was practiced by the Prophet (peace and blessings be upon him) and he encouraged Muslims to practice it.
2- It is permissible, according to the majority of Muslim scholars, to make up for a missed witr Prayer. However, there is a difference of opinion over what time it may be made up.
Shedding more light on your question, Sheikh Sayyed Sabiq, the well-known Azharite scholar and the author of “Fiqh As-Sunnah” states:
The majority of scholars maintain that it is permissible to make up for a missed witr prayer. Abu Hurairah (may Allah be pleased with him) reported that the Prophet (peace and blessings be upon him) said, “If the morning approaches, and you have yet to pray witr, you should pray the witr Prayer.” (Al-Baihaqi)
Abu Dawud reported on the authority of Abu Sa`id Al-Khudri that the Prophet (peace and blessings be upon him) said, “If one of you sleeps (and thus misses) the witr Prayer or forgets it, he should pray it when he remembers it.” (Abu Dawud)
Generally speaking, there is a difference of opinion over what time it may be made up. The Hanafi jurists hold the view that it should be performed during those times in which it is not forbidden to perform prayer.
The Shafi`is, however, maintain that it may be made up during any time of the night or day, while, according to both Imam Malik and Imam Ahmad, a missed witr Prayer is to be made up for after Fajr.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.