The Messenger of Allah ﷺ said, "Five practices are part of the natural disposition: trimming the moustache, clipping the nails, plucking the underarm hair, shaving the pubic hair, and circumcision."
حدثنا معتمر عن معمر عن الزهري عن سعيد بن المسيب
قال رسول الله ﷺ خمس من الفطرة قص الشارب وتقليم الأظفار ونتف الإبط والاستحداد والختان
Its isnad is sahih. Mutamir is Ibn Sulayman Taymi. Mamar is Ibn Rashid Haddani. The hadith was narrated by the group, as in al-Muntaqa no. 184.Regarding istihdad, Ibn Athir said, it is shaving the pubic hair with an iron blade.