Ascetic

As·cet·ic

Ascetic

a.
  1. Extremely rigid in self-denial and devotions; austere; severe.
    The stern ascetic rigor of the Temple discipline.

Ascetic

n.
  1. In the early church, one who devoted himself to a solitary and contemplative life, characterized by devotion, extreme self-denial, and self-mortification; a hermit; a recluse; hence, one who practices extreme rigor and self-denial in religious things.
    I am far from commending those ascetics that take up their quarters in deserts.
    — Norris.

Phrases & Compounds

Ascetic theology
the science which treats of the practice of the theological and moral virtues, and the counsels of perfection.