The Instruction and Benefit of Fasting

Quotidiano enim, dilectissimi, experimento probatur satietate carnis aciem mentis obtundi, et ciborum nimietate vigorem cordis hebetari, ita ut delectatio edendi etiam corporum contraria sit saluti, nisi ratio temperantiae obsistat illecebrae, et quod futurum est oneri, subtrahat voluptati. Quamvis enim sine anima nihil caro desideret, et inde accipiat sensus unde sumit et motus; ejusdem tamen est animae, quaedam subditae sibi negare substantiae, et interiori judicio, ab inconvenientibus exteriora frenare, ut a corporeis cupiditatibus saepius libera, in aula mentis possit divinae vacare sapientiae, ubi omni strepitu terrenarum silente curarum, in meditationibus sanctis, et in deliciis laetetur aeternis. Quod etsi in hac vita difficile est continuari, potest tamen frequenter assumi, ut saepius ac diutius spiritalibus potius quam carnalibus occupemur; et cum melioribus curis majores impendimus moras, ad incorruptibiles divitias, etiam temporales transeant actiones. Hujus observantiae utilitas, dilectissimi, in ecclesiasticis praecipue est constituta jejuniis, quae ex doctrina sancti Spiritus ita per totius anni circulum distributa sunt, ut lex abstinentiae omnibus sit ascripta temporibus. Siquidem jejunium vernum in Quadragesima, aestivum in Pentecoste, autumnale in mense septimo, hiemale autem in hoc qui est decimus celebramus, intelligentes divinis nihil vacuum esse praeceptis, et verbo Dei ad eruditionem nostram omnia elementa servire; dum per ipsius mundi cardines, quasi per quatuor Evangelia, incessabiliter discimus quod et praedicemus et agamus. Sanctus Leo Magnus, Sermo XIX

Indeed, beloved, by daily experience it is proved that the mind's edge is blunted by indulgence of the flesh and the heart's vigour is dulled by excess of food, so that the delights of eating are actually opposed to the health of the body unless reasonable temperance resists enticement and prospect of future burdens draws us from pleasure. Although without the soul the flesh desires nothing, and from whence it receives its sense so it receives its motions, yet it is of the same soul to deny certain things to the matter which is subject to it and by interior judgment to restrain the exterior from things inconvenient, that it may be more often liberated from bodily desires and in the palace of the mind have leisure for Divine wisdom, where, all clamor of earthly cares being silent, it may rejoice in sacred meditations and eternal delights. And even though in this life it is is difficult to maintain, yet one can frequently take up the task again, that we may more often and for longer be occupied with spiritual rather than bodily cares, and that by devoting ever greater time to higher cares even our temporal actions may pass to incorruptible riches. So this useful observance, dearly beloved, is especially established for the fasts of the Church, which, by the teaching of the Holy Spirit, are distributed over the whole course of the year that the law of abstinence may be present at all times. Thus it is we practise the spring fast in Lent, the summer fast at Pentecost, the autumn fast in the seventh month, and the winter fast in the tenth month, knowing that there is nothing lacking in the Divine commands and that to our instruction all the elements serve the Word of God, while on the very hinges on which the world turns, as if on the four Gospels, we learn unceasingly what to preach and to do. Saint Leo the Great, Sermon 19