Five are acts of Fitrah (natural disposition): circumcision, shaving the pubic hair, trimming the mustache, clipping the nails, and plucking the armpit hair
Abu Hurayrah (may Allah be pleased with him) reported: I heard the Prophet (may Allah's peace and blessings be upon him) say:
"Five are acts of Fitrah (natural disposition): circumcision, shaving the pubic hair, trimming the mustache, clipping the nails, and plucking the armpit hair."
«الفِطْرَةُ خمسٌ: الخِتَانُ والاستحدادُ وقصُّ الشَّارِبِ وتقليمُ الأظفارِ وَنَتْفُ الآبَاطِ».
The Prophet (may Allah's peace and blessings be upon him) mentioned five acts that belong to the religion of Islam and the practices of the messengers. First: Circumcision: This is to cut the foreskin of the glans of the male organ and to cut the tip of a female's clitoris. Second: Shaving the pubes. This is to cut the pubic hair, which grows around the sex organs. Third: trimming the mustache. This is to trim the hair that grows on a man's upper lip in a way that makes the lip visible. Fourth: Clipping the nails. Fifth: Plucking the armpit hair.
...:
The messengers' practices that Allah likes, is pleased with, and enjoins lead to perfection, purity, and beauty.
The legitimacy of observing these acts and not overlooking them.
These acts serve religious and worldly benefits, such as: improving appearance, cleaning the body, being heedful about purification, differing from the disbelievers, and complying with the commands of Allah.
Other Hadīths mention more acts of the Fitrah other than these five, like letting the beard grow and using the tooth-stick.
Sahīh Al-Bukhāri (7/ 160) (5891).
Sahīh Muslim (1/ 222) (257).
More (7)
عمدة الأحكام (ص44) (30).
الإلمام بشرح عمدة الأحكام.
لإسماعيل الأنصاري (1/ 45).
تيسير العلام شرح عمدة الأحكام.
للبسام (ص58).
تنبيه الأفهام شرح عمدة الأحكام.
لابن عثيمين (1/ 72).