Uposatha - Uposatha

…There is also a festival called “Shou” for the purpose of warding off evil spirits. This is a way of worshiping the gods by laying out offerings at night and making prayers. Taoist festivals are sometimes called “Sai” together. Since “Sai” means “purity”, in Buddhism it is used as a translation of uposatha or poṣadha (transliterated as “fusatsu”) to mean observing the precepts and purifying the body. On the six fasting days, that is, the 8th, 14th, 15th, 23rd, 29th, and 30th of each month, lay believers were required to observe the “Eight Fasting Precepts”. These refer to eight types of taboos such as not killing, not stealing, and not committing sexual acts. Among them, “non-time eating”, that is, fasting in the afternoon, was the focus, and in Buddhism it mainly meant eating in the morning. …

*Some of the terminology explanations that mention "Uposatha" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…また厄よけを目的とする〈醮（しよう）〉という祭りもあり，これは夜間に供物を並べて神々を祭り，願いごとを上奏するやり方で，道教の祭りは両者を合して〈斎醮〉とよばれることもある。　斎は清浄の意味をもつから，仏教でもウポサタuposathaまたはポシャダpoṣadha(音訳は布薩（ふさつ）)の訳語として戒律を守り，身を清める意味に用いられ，六斎日（ろくさいにち），すなわち毎月8,14,15,23,29,30の6日には，在家の信者は〈八斎戒〉を守らねばならぬとされた。それは，殺さず，盗まず，婬せずなどの8種の禁忌をいうが，なかでも〈非時食（ひじしき）〉，すなわち午後の断食が中心とされ，仏教では主として午前中の食事を意味することになった。…

※「ウポサタ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報