The Messenger of Allah ﷺ set a limit for us regarding trimming the moustache, clipping the nails, and shaving the pubic hair, that it should be done once every forty days.
حدثنا يزيد أخبرنا صدقة بن موسى عن أبي عمران الجوني
وقت لنا رسول الله ﷺ في قص الشارب وتقليم الأظفار وحلق العانة في كل أربعين يوما مرة
Its isnad is sahih. Abu Imran Jawni is Abdul-Malik bin Habib Azdi, who is trustworthy. Sadaqah bin Musa's hadith here is sahih, and his lapses are few, something no one is free of. The hadith was narrated by Muslim, 1/222, in the Book of Purification, on the characteristics of fitrah, by Abu Dawud in the Book of Trimming the Hair, 4/84, number 4200, by Nasai in the Book of Purification, 1/16, number 14, and by Ibn Majah, 1/108, number 295, similarly to Muslim.