What is the prescribed manner (unit of rak'ahs) for performing voluntary (Nafl) night prayers and day prayers?
Chapter on the Times When Prayer is Prohibited
Al-Mughni
Book of Prayer
Primary text
Voluntary night prayer must be performed in units of two rak'ahs (Mathna Mathna). This is the position held by the majority of scholars, including Abu Yusuf and Muhammad. The basis for this ruling is the authenticated saying of the Prophet (peace be upon him), "The prayer of the night is two by two," and the statement that the separator between every two rak'ahs is a Taslimah. For day prayers, the general ruling is that they should also be performed in units of two rak'ahs, supported by a narration stating, "The prayer of the night and the day is two by two." This is considered preferable as it reduces the chance of error and resembles the night prayer, and the Prophet's confirmed voluntary prayers were two rak'ahs.
Supporting text
Abu Hanifa holds that one may pray two, four, six, or eight rak'ahs for night prayers. Regarding day prayers, some scholars, including Ishaq, Al-Awza'i, and the Ashab al-Ra'y, suggest that four rak'ahs are preferable, citing a hadith about four rak'ahs before Dhuhr having their doors of heaven opened. Another argument suggests that the limiting of night prayer to two implies day prayer can be in fours. However, the preferred view remains two rak'ahs for the day.