How much sleep does a person need at night?
The Rambam[1] writes that one is to sleep at night for one third of the day, which is a period of eight hours. In other Sefarim[2] it states that one is required to sleep four hours. Practically the Poskim[3] conclude that the amount of sleep one needs varies in each person, and each person is to sleep enough time that he have a clear and calm mind for learning Torah and serving Hashem.[4] The Yaavetz[5] writes that a healthy person can sleep for six hours a night and this is dependent on one’s sleeping habits that he acquired. The older one becomes the less sleep he requires.[6]
[1] Hilchos Deios 4:4
[2] Ashel Avraham Butchach 1; Mahram Schik 1
[3] M”A 238; M”B 238:2; Taz Even Haezer 25:1
[4] Taz ibid
[5] In his Siddur under the section of the bedtime Shema; See also Maggid Dvarav Leyaakov Hosafos p. 47 for a letter that the Maggid wrote to his son Avraham in which he states to his son that he sould sleep not less than six hours per night.
[6] See Tiferes Yisrael Avos 6:83