SALATU ‘T-TARAWIH. صلاة التراوة
“Prayer of rest.” So called because of the pause or rest made for ejaculations between every four rak’ahs. (‘Abaa l’-Haqq.)
Twenty rak’ah prayers recited after the night prayer during the month of Ramazan. They are often followed with recitations known as zitkrs [ZIKR.], and form an exciting service of devotion. The Imam recite the Tarawik prayers with a loud voice.
Abu Hurairah says “The Prophet used to encourage people to say night prayers in Ramazan without ordering them positively, and would say. He who stands up in prayer at night for the purpose of obtaining reward, will have all his sins pardoned'; then the Prophet died, leaving the prayers of Ramazan in this way.” It is said ‘Umar instituted the present custom of reciting the twenty rak’ahs. (Mishkat, book iv ch. xxxviii.) [RAMAZAN.]
Based on Hughes, Dictionary of Islam