from the Prophet ﷺ, that he ﷺ fixed the time as every forty nights for them to trimming the fingernails, taking from the mustache, and shaving the pubic hairs.
عَنِ النَّبِيِّ ﷺ أَنَّهُ وَقَّتَ لَهُمْ فِي كُلِّ أَرْبَعِينَ لَيْلَةً تَقْلِيمَ الأَظْفَارِ وَأَخْذَ الشَّارِبِ وَحَلْقَ الْعَانَةِ