What is the ruling on the night prayer (Qiyam al-layl)?

Night vigil (Qiyam al-Layl) is a confirmed Sunnah, observed from after the 'Isha prayer until the emergence of dawn. Allah has praised those who perform it and promised them Paradise, as He states: "Their sides forsake their beds, they call upon their Lord in fear and aspiration, and from what We have provided them, they spend. No soul knows what has been hidden for them of comfort for eyes, as reward for what they used to do." The Prophet, peace be upon him, encouraged it, even if for a duration equivalent to milking a camel. The minimum is one rak'ah of Witr, and it is preferable to conclude with Witr, in compliance with his saying, peace be upon him: "Make the last of your prayer at night Witr."