Jihaad:

Hazrat Sa’d (radhiyallahu ‘anhu) had mentioned, “I participated in the Battle of Badr at a time when I had only one strand of hair on my face. Later on, Allah Ta‘ala blessed me with a beard.

(ibn Sa’d 3/105, Siyar A’laam min Nubalaa 3/62)

Hazrat Sa’d (radhiyallahu ‘anhu) had participated in the Battles of Badr and Uhud, and he was among the Sahaabah (radhiyallahu ‘anhum) who remained firm with Rasulullah (sallallahu ‘alaihi wasallam) during the Battle of Uhud when (the enemy attacked from the rear and killed many Sahaabah (radhiyallahu ‘anhum), due to which there was much confusion and) many Sahaabah (radhiyallahu ‘anhum) turned away from the battlefield.