The Vigil in the Depth of Night

Tahajjud is the voluntary night prayer of Islam, offered after a period of sleep in the last part of the night before dawn. It is not among the five obligatory prayers, but it holds a place of exceptional honour in the tradition, praised in the Qur'an where the Prophet Muhammad is directed to keep vigil in a portion of the night as an additional devotion, and where those who forsake their beds to call upon their Lord are commended. The name derives from a root meaning to remain awake, and the practice is defined by its cost: rising in the stillness when sleep would be natural, precisely because that hardship is understood to make the worship sincere.

There is no fixed number of units. The reported practice of the Prophet was a small number of long, unhurried rak'ah with extended recitation, standing and prostration. Worshippers add supplication and, often, the reading of the Qur'an, and the hour is held in the sources to be the time when prayer is most surely heard, the divine mercy described as descending upon the world in the last third of the night.