Night prayer consists of eight units (rak'ahs), two units of Shaf' (pair) prayer, one unit of Witr, and two units before Fajr, making a total of fifty-one units of prayer in a day and night. Whoever reaches the last part of the night and performs the Witr prayer along with the night prayer does not need to count the two units performed while sitting after the last Isha prayer. The prayers, therefore, amount to fifty units in a day and night. It is fifty units because there are twelve hours in the night and twelve hours in the day, and between the rising of the dawn and the rising of the sun, there is one hour. Thus, Allah سبحانه وتعالى, the Mighty and Majestic, ordained two units for each hour.