Witr is the odd-numbered prayer that closes the night prayer. The word witr means odd. Its time begins after the Isha prayer and lasts until Fajr. Many Muslims pray it as three rak'ahs after Isha, but the reports allow more than one form.

Ibn Umar reported that when someone asked about the night prayer, the Prophet, peace be upon him, replied that it is offered two rak'ahs followed by two rak'ahs, and that whoever fears the approaching dawn should pray one rak'ah, which makes an odd number of all he has prayed. This is in Sahih al-Bukhari, number nine hundred and ninety. The Prophet also said to make Witr the last of your prayers at night, in Sahih al-Bukhari, number nine hundred and ninety-eight. And Aisha reported that he prayed Witr at different hours of the night, up to the last hour, in Sahih al-Bukhari, number nine hundred and ninety-six.

So, in practice: pray Witr after Isha and before Fajr. If you plan to pray at night, make Witr your last prayer. If you do not expect to wake, pray it before sleeping.

Scholars differ on several details. On its status, the Hanafi school regards Witr as wajib, a strong obligation just below the obligatory prayers, while the majority of scholars, in the Maliki, Shafi'i and Hanbali schools, regard it as a strongly recommended sunnah. On its form, the Hanafi school prays three rak'ahs with a single salam at the end, while the other schools allow one, three, or more rak'ahs, with a salam after the first two if desired. And the schools differ on whether a particular supplication, known as qunut, is said in Witr, at what time of year, and whether before or after bowing.

Learn from your teacher which form you follow. In every school, Witr is a prayer the Prophet was keen on, and one worth guarding.