Five are the acts quite akin to the Fitra, or five are the acts of Fitra: circumcision, shaving the pubes, cutting the nails, plucking the hair under the armpits and clipping the moustache.
The Book of Purification
Sahih Muslim 257a
Exposition of the Hadith
This noble hadith enumerates five practices that are from the primordial nature (fitra) upon which Allah created mankind. These acts purify the body and conform to the innate disposition that Allah has ordained for His servants.
Circumcision (khitan) is a sunnah for men and an honor for women. It purifies the body and facilitates cleanliness. Shaving the pubic hair removes impurities and maintains hygiene. Cutting the nails prevents the accumulation of dirt and germs. Plucking the armpit hair eliminates odor and promotes purity. Clipping the moustache ensures that food and drink are not contaminated, and it distinguishes the believer from the polytheist.
These practices should be performed regularly: trimming the moustache and nails weekly, and removing pubic and armpit hair at least every forty days, as established in other narrations. They are manifestations of Islamic cleanliness and reflect the comprehensive nature of the Shari'ah in guiding believers to purity in both spiritual and physical realms.