It is narrated from Sayyiduna Thawban (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "Indeed, staying awake is hardship and a burden, so when any of you has performed Witr, then let him perform two more rak‘ahs after it. If he wakes up during the night, then fine; otherwise, these two rak‘ahs will be counted as his night prayer (qiyam al-layl)." Instead of «هٰذا السهر» , «‏‏‏‏ «هٰذا السفر» has also been said, but I say «هٰذا السهر» only, meaning to wake up after sleeping.