It was narrated from 'Ammar bin Yasir that: The Messenger of Allah said: "Part of the Fitrah is rinsing out the mouth, rinsing out the nostrils, using the tooth stick, trimming the mustache, clipping the nails, plucking the armpit hairs, shaving the pubic hairs, washing the joints, washing the private parts and circumcision'." (Da'if) Another chain with similar wording.
These teachings also remind us that we should take pride in ourselves by taking care of how we look on the outside too. We should strive to present ourselves with dignity at all times by keeping up with good hygiene habits such as brushing teeth regularly or trimming facial hair when necessary. This is an important reminder for everyone regardless if they are young or old because it helps promote self-respect which is essential for living a meaningful life according to Islamic teachings.