Question Summary:
I missed my Witr. What should I do?

Question Detail:

Assalāmualaikum. What shall a person do if he missed Salātul Witr?  If one prays Qiyāmul Layl every night and he usually prays Witr also in Qiyām but misses it one day what should he do?  Is it necessary to do Qadhā of Witr if a person misses it?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful. 
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
The performance of Salāt al-Witr is Wājib (necessary). Hence it is necessary to do Qadhā of Salāt al-Witr.  
If one is not confident that he/she will wake up in the latter part of the night to offer Salāt al-Witr, then it should be performed before sleeping.  Since it is such an emphasized prayer, one should not risk its performance by sleeping before offering Salāt al-Witr if one is unsure or doubtful of waking up to perform Qiyām al-Layl.  [1]
And Allah Ta’āla Knows Best
Mawlana Abdul Azīm bin Abdur Rahman,
Student Darul Iftaa
US 
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net