St. Jerom, in strong but indiscreet language, expresses the most important use of fasting and abstinence:
"Non quod Deus universitatis Creator et Dominus, intestinorum nostrorum rugitu, et inanitate ventris, pulmonisque ardore delectetur, sed quod aliter pudicitia tuta esse non possit." (Op. tom. i. p. 137, ad Eustochium [Ep. 22, tom. i. p. 94, ed. Vallars.].)
See the twelfth and twenty-second Collations of Cassian, de Castitate and de Illusionibus Nocturnis.