غسل الجمعة
A recommended full-body wash before the Friday congregational prayer, described as an obligation upon every adult.
غُسْلُ الْجُمُعَةِ وَاجِبٌ عَلَى كُلِّ مُحْتَلِمٍ
“Friday's ritual bath is obligatory upon every adult.” (meaning, not a literal translation)
Other narrations tie this specifically to the crowded conditions of the early Friday congregation — 'Umar is reported to have publicly reminded a companion of this obligation when he arrived at the mosque without having washed, showing it was actively enforced as a communal courtesy as well as a personal one.
Commentators note the practical hygiene benefit of a guaranteed weekly full wash in a society without daily home bathing infrastructure — alongside its ritual purpose. Ibn al-Qayyim discusses this as complementing the daily partial ablution (wudu) required before each prayer, with the weekly full-body wash addressing what the more frequent partial washing doesn't cover.
Regular full-body bathing is uncontroversial modern hygiene practice; the specific weekly-minimum structure here reflects historical bathing infrastructure limitations rather than a claim that weekly is the ideal modern frequency, which most people now exceed as a matter of course.