What is the prescribed time for performing voluntary (Nafl) prayers?

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Voluntary prayers are permissible throughout the entire night. During the day, they are permissible except during times specifically prohibited for voluntary prayer. The voluntary prayer performed at night is superior to that performed during the day. Ahmad holds that no act is more meritorious after the obligatory prayers than the night vigil (Qiyam al-Layl). This is supported by the command given to the Prophet, peace be upon him, in the Quran: "And during a portion of the night, keep awake for it as an additional prayer for you" (Quran 17:79). Furthermore, Abu Hurairah narrated that the Messenger of Allah said: "The best prayer after the obligatory prayer is the night prayer," which Al-Tirmidhi graded as Hasan (good).