adjective
penitential
pen-ih-TEN-shul/ˌpenɪˈtenʃl/
Expressing or relating to repentance for wrongdoing.
The kneeling person's penitential posture expresses repentance beside the cross.

Etymology
The adjective connects repentance with things that express or enact it. Its early sense, “done as penance,” shows how inward regret could be expressed through acts intended to make amends.
In context
one of the Carmelite penitential practices
More examples
- The congregation kneels for a penitential prayer.
- He adopts a penitential tone when he admits his mistake.
- Lent is a penitential season of reflection and self-denial.