Know, brothers and sisters, that the best obligation after believing properly in Allaah and His Messenger is to perform the five obligatory prayers: DHuhr, ^ASr, Maghrib, ^Ishaa’ and Fajr. The high reward of praying carries onto the recommendations as well: If one wanted to choose between fasting a recommended fast or praying recommended prayers, it would be better for him to perform those recommended prayers. Among the recommended prayers one can complete on a daily basis is the Witr prayer.
The best recommended prayer that one can perform on a daily basis is witr. Its time starts after one pray ^Ishaa. So even if ^Ishaa time is in, if one has not prayed ^Ishaa one cannot pray witr. Its time lasts until Fajr. Witr is typically the last prayer one performs before Fajr comes in.
Witr is prayed in odd numbers. The scholars said one is allowed, three is better than one, five is better than three, and seven is better than five. Some scholars mentioned a maximum of 11, others 13, and others refused to give a maximum.
According to the Shaafi^iyy school, witr is an emphasized sunnah. Some scholars mentioned that praying it is an obligation, but not on the same level as the five obligatory prayers. The Prophet would never leave it out, so it is a good habit to have.
Important Note: One does not perform recommended prayers if they have obligatory prayers to make up. They must first spend all their time making up those obligatory prayers, because they come prior.