Now, if there has been temerity in our retracing to primordial experiences the reasons for God’s having laid, and our duty (for the sake of God) to lay, restrictions upon food, let us consult common conscience. Nature herself will plainly tell with what qualities she is ever want to find us endowed when she sets us, before taking food and drink, with our saliva still in a virgin state, to the transaction of matters, by the sense especially whereby things divine are, handled; whether (it be not) with a mind much more vigorous, with a heart much more alive, than when that whole habitation of our interior man, stuffed with meats, inundated with wines, fermenting for the purpose of excremental secretion, is already being turned into a premeditatory of privies, (a premeditatory) where, plainly, nothing is so proximately super-sequent as the savoring of lasciviousness. “The people did eat and drink, and they arose to play.” (Cf. 1Co_10:7 with Exo_32:6.) Understand the modest language of Holy Scripture: “play,” unless it had been immodest, it would not have reprehended. On the other hand, how many are there who are mindful of religion, when the seats of the memory are occupied, the limbs of wisdom impeded? No one will suitably, fitly, usefully, remember God at that time when it is customary for a man to forget his own self. All discipline food either slays or else wounds. I am a liar, if the Lord Himself, when upbraiding Israel with forgetfulness, does not impute the cause to “fullness:” “(My) beloved is waxen thick, and fat, and distant, and hath quite forsaken God, who made him, and hath gone away from the Lord his Savior.” (Deu_32:15) In short, in the self-same Deuteronomy, when bidding precaution to be taken against the self-same cause, He says: “Lest, when thou shalt have eaten, and drunken, and built excellent houses, thy sheep and oxen being multiplied, and (thy) silver and gold, thy heart be elated, and thou be forgetful of the Lord thy God.” (Deu_8:12-14) To the corrupting power of riches He made the enormity of edacity antecedent, for which riches themselves are the procuring agents. Through them, to wit, had “the heart of the People been made thick, lest they should see with the eyes, and hear with the ears, and understand with a heart” (Isa_6:10; Joh_12:40; Act_28:26, Act_28:27) obstructed by the “fats” of which He had expressly forbidden the eating, (Lev_3:17) teaching man not to be studious of the stomach. (Deu_8:3; Mat_4:4; Luk_4:4)
On the other hand, he whose “heart” was habitually found “lifted up” (Psa_86:4, Psa_85:4); (Lam_3:41) (Lam_3:40 LXX) rather than fattened up, who in forty days and as many nights maintained a fast above the power of human nature, while spiritual faith sub ministered strength (to his body), both saw with his eyes God’s glory, and heard with his ears God’s voice, and understood with his heart God’s law: while He taught him even then (by experience) that man liveth not upon bread alone, but upon every word of God; in that the People, though fatter than he, could not constantly contemplate even Moses himself, fed as he had been upon God, nor his leanness, sated as it had been with His glory! (Exo_33:18, Exo_33:19), with (Exo_34:4-9, Exo_34:29-35)
Deservedly, therefore, even while in the flesh, did the Lord show Himself to him, the colleague of His own fasts, no less than to Elijah. (Mat_17:1-13; Mar_9:1-13; Luk_9:28-36) For Elijah withal had, by this fact primarily, that he had imprecated a famine, (Jam_5:17) already sufficiently devoted himself to fasts: “The Lord liveth,” he said, “Before whom I am standing in His sight, if there shall be dew in these years, and rain-shower.” (1Ki_17:1)(3 Kings, LXX)) Subsequently, fleeing from threatening Jezebel, after one single (meal of) food and drink, which he had found on being awakened by an angel, he too himself, in a space of forty days and nights, his belly empty, his mouth dry, arrived at Mount Horeb; where, when he had made a cave his inn, with how familiar a meeting with God was he received! “What (doest) thou, Elijah, here?” (1Ki_19:9, 1Ki_19:13.) Much more friendly was this voice than, “Adam, where art thou?” (Gen_3:9, LXX) For the latter voice was uttering a threat to a fed man, the former soothing a fasting one. Such is the prerogative of circumscribed food, that it makes God tent-fellow (Cf. Mat_17:4; Mar_9:5; Luk_9:33) with man – peer, in truth, with peer! For if the eternal God will not hunger, as He testifies through Isaiah, this will be the time for man to be made equal with God, when he lives without food.
VII. – Further Examples from the Old Testament in Favor of Fasting
And thus we have already proceeded to examples, in order that, by its profitable efficacy, we may unfold the powers of this duty which reconciles God, even when angered, to man.
Israel, before their gathering together by Samuel on occasion of the drawing of water at Mizpeh, had sinned; but so immediately do they wash away the sin by a fast, that the peril of battle is dispersed by them simultaneously (with the water on the ground). At the very moment when Samuel was offering the holocaust (in no way do we learn that the clemency of God was more procured than by the abstinence of the people), and the aliens were advancing to battle, then and there “the Lord thundered with a mighty voice upon the aliens, and they were thrown into confusion, and felt in a mass in the sight of Israel; and the men of Israel went forth out of Mizpeh, and pursued the aliens, and smote them unto Bethor,” – the unfed (chasing) the fed, the unarmed the armed. Such will be the strength of them who “fast to God.” (Zec_7:5) For such, Heaven fights. You have (before you) a condition upon which (divine) defense will be granted, necessary even too spiritual wars.
Similarly, when the king of the Assyrians, Sennacherib, after already taking several cities, was volleying blasphemies and menaces against Israel through Rabshakeh, nothing else (but fasting) diverted him from his purpose, and sent him into the Ethiopia’s. After that, what else swept away by the hand of the angel an hundred eighty and four thousand from his army than Hezekiah the king’s humiliation? if it is true, (as it is), that on hearing the announcement of the harshness of the foe, he rent his garment, put on sackcloth, and bade the elders of the priests, similarly habited, approach God through Isaiah – fasting being, of course, the escorting attendant of their prayers. (2Ki_18:1-37, 2Ki_19:1-37; 2Ch_32:2; Isa_36:1-22, Isa_37:1-38) For peril has no time for food, nor sackcloth any care for satiety’s refinements. Hunger is ever the attendant of mourning, just as gladness is an accessory of fullness.
Through this attendant of mourning, and (this) hunger, even that sinful state, Nineveh, is freed from the predicted ruin. For repentance for sins had sufficiently commended the fast, keeping it up in a space of three days, starving out even the cattle with which God was not angry. Sodom also, and Gomorrah, would have escaped if they had fasted. (Eze_16:49; Mat_11:23, Mat_11:24; Luk_10:12-14) This remedy even Ahab acknowledges. When, after his transgression and idolatry, and the slaughter of Naboth, slain by Jezebel on account of his vineyard, Elijah had upbraided him, “How hast thou killed, and possessed the inheritance? In the place where dogs had licked up the blood of Naboth, thine also shall they lick up,” – he “abandoned himself, and put sackcloth upon his flesh, and fasted, and slept in sackcloth. And then (came) the word of the Lord unto Elijah, Thou hast seen how Ahab hath shrunk in awe from my face: for that he hath shrunk in awe I will not bring the hurt upon (him) in his own days; but in the days of his son I will bring it upon (him)” – (his son), who was not too fast. (1Ki_21:1-29 (3 Ki_20, LXX)) Thus a God-ward fast is a work of reverential awe: and by its means also Hannah the wife of Elkanah making suit, barren as she had been before time, easily obtained from God the filling of her belly, empty of food, with a son, ay, and a prophet. (1Sa_1:1, 1Sa_1:2, 1Sa_1:7-20, 1Sa_3:20 (1 Kings, LXX))
Nor is it merely change of nature, or aversion of perils, or obliteration of sins, but likewise the recognition of mysteries, which fasts will merit from God. Look at Daniel’s example. About the dream of the King of Babylon all the sophists are troubled: they affirm that, without external aid, it cannot be discovered by human skill. Daniel alone, trusting to God, and knowing what would tend to the deserving of God’s favor, requires a space of three days, fasts with his fraternity, and – his prayers thus commended – is instructed throughout as to the order and signification of the dream; quarter is granted to the tyrant’s sophists; God is glorified; Daniel is honored; destined as he was to receive, even subsequently also, no less a favor of God in the first year, of King Darius, when, after careful and repeated meditation upon the times predicted by Jeremiah, he set his face to God in fasts, and sackcloth, and ashes. For the angel, withal, sent to him, immediately professed this to be the cause of the Divine approbation: “I am come,” he said, “to demonstrate to thee, since thou art pitiable” (Dan_9:23, Dan_10:11) – by fasting, to wit. If to God he was “pitiable,” to the lions in the den he was formidable, where, six days fasting, he had breakfast provided him by an angel.
~Tertullian- On Fasting Vol. 1