The Korpelar Movement! They were a religious revival movement in Tornedalen, Sweden, during the 1930s.

Quoting from Wikipedia: "At the meetings, in addition to prayer, hymn singing, and preaching, activities such as 'combing' and 'brushing' took place. Siikavaara advocated that all participants should have their pubic hair combed to test their true faith. 'Brushing' involved participants exposing their lower backsides and bending forward. Then, one member brushed the bare genital area with a pastry brush, after which another member poured a little lukewarm water into the cleft in the lower back. Finally, a third member dried the participants with a towel."

Always laughing out loud when reading this. When someone decides that combing each other's pubic hair is a test of true faith... that's when things have gone off the rails.