The case has to be made properly, which means not making it as a list of verses that happen to mention fasting. Anyone can assemble such a list and it proves very little, since Scripture also mentions a great many things it does not command. The Orthodox claim is structural, and it has four parts: that fasting is assumed throughout Scripture as a normal action of God's people rather than an exception requiring justification; that Christ fasted, and fasted first, before anything else in His public life; that when He taught on the subject He legislated the manner of it and not the fact of it, in the same breath and the same grammar as prayer and almsgiving; and that He said explicitly that His disciples would fast once He was taken away, which the apostolic Church in Acts is then shown doing at its most consequential moments. Each of those can be tested against the text.
Begin where the Gospels begin. Immediately after the baptism, Christ is led by the Spirit into the wilderness, and He fasts forty days and forty nights, and afterward He is hungry (Matthew 4:1–2; Luke 4:1–2). Two things in that are easy to read past. The first is the order: the first thing the Spirit leads Him to do after the descent at the Jordan is to go without food, and the first assault the devil makes is on the stomach. The second is the shape of it. Forty days is not an arbitrary number in that sentence; it is Moses on the mountain, who was there with the Lord forty days and forty nights and neither ate bread nor drank water (Exodus 34:28), and Elijah, who went in the strength of one meal forty days and forty nights to Horeb (3 Kingdoms 19:8 [1 Kings 19:8]), and behind both of them Israel's forty years. The Lenten forty is patterned on Christ's rather than the other way round. And it should be conceded at once that His fast was total, and that the Church has never required a total fast of forty days from anybody, which is a real difference and not a small one.
When you fast
The decisive passage is short, and its force is grammatical. In the Sermon on the Mount, Christ takes three practices in sequence and treats them identically: almsgiving (Matthew 6:2–4), prayer (6:5–15), fasting (6:16–18). Each is introduced the same way. When you do a charitable deed. When you pray. When you fast. The Greek in each case is hotan with the subjunctive, the ordinary construction for something that will happen and whose timing is open — not ei, the word for a genuine conditional. He nowhere commands any of the three. He assumes all three, and what He legislates is the manner: do not do it to be seen, do not sound a trumpet, do not disfigure your face, and He gives the same warning and the same promise in the same words to all three, that the Father who sees in secret will reward openly.
The consequence is awkward and should be faced squarely. No Protestant reads when you pray as optional, and none reads when you give as optional; both are treated as descriptions of what a Christian does, and rightly. The middle member of the triad, standing between them in the same sermon and introduced by the same word, is the one that is read as a Jewish survival that lapsed with the old covenant. There is nothing in the text that permits the distinction. Christ's instruction in verse 17 makes it worse for that reading rather than better: anoint your head and wash your face, so that your fasting is not seen by men. An instruction about how to conceal an act presupposes the act. He is not telling His disciples whether to fast. He is telling them to stop performing it.
Then Matthew 9:14–15, with its parallels at Mark 2:18–20 and Luke 5:33–35, which is the passage most often cited on the other side. John's disciples come and ask why they and the Pharisees fast while Christ's disciples do not. His answer is not that fasting is finished. It is that it is suspended, and He gives the reason and the end date: can the friends of the bridegroom mourn as long as the bridegroom is with them? But the days will come when the bridegroom will be taken away from them, and then they will fast. That is a future indicative about His own disciples. Whatever else the verse does, it forbids the reading that fasting belongs only to the period before Christ. And it is worth noticing that the Orthodox calendar is constructed out of precisely that distinction: Wednesday and Friday, the betrayal and the Cross, are fast days, and Bright Week, the week in which the Bridegroom is most emphatically present, is a week on which fasting is forbidden outright, Wednesday and Friday included — as is the week after Pentecost. Through the rest of the paschal season the two weekly days return, relaxed rather than cancelled. A reader may reject the calendar. He should at least see that it is an attempt to obey that sentence rather than to evade it.
A verse to leave alone
There is one famous text that an honest treatment has to hand back. In Mark 9, after the disciples fail to cast out a spirit, Christ tells them that this kind can come out by nothing but prayer and fasting (Mark 9:29). The words and fasting are absent from the earliest surviving manuscripts, including Codex Sinaiticus in its original hand and Codex Vaticanus, and present in the great majority of later ones. They stand in the Byzantine text, which is the text the Orthodox lectionary reads, and the New King James Version therefore prints them. Matthew's parallel verse, 17:21, is missing from the earliest manuscripts altogether. Modern critical editions omit both. This is a genuine textual question, not a conspiracy in either direction, and the right response is not to build anything on it. The case for fasting stands entirely without Mark 9:29, and an argument that leans on a disputed reading deserves the treatment it will get.
The variant is nonetheless evidence of something, and of something relevant. The same pattern appears at 1 Corinthians 7:5 and Acts 10:30, where later manuscripts add fasting to a text about prayer. Whoever made those additions was not forging a doctrine; he was copying in a Church for which prayer and fasting had become a single phrase, so habitually joined that a scribe's hand supplied the second word when his eye saw the first. That tells us nothing about what Mark wrote and a good deal about the Christians of the second, third and fourth centuries who copied him.
The apostolic Church
Acts shows the Church fasting twice, and both times at a moment of maximum consequence. At Antioch, while the prophets and teachers ministered to the Lord and fasted, the Holy Spirit said, Now separate to Me Barnabas and Saul for the work to which I have called them; and then, having fasted and prayed and laid hands on them, they sent them away (Acts 13:2–3). Later, at the end of the first journey, Paul and Barnabas appointed elders in every church, and prayed with fasting, and commended them to the Lord (Acts 14:23). Both are corporate, not private; both attend the setting apart of men for ministry; and the second is a practice being repeated in every church they had founded. There is also a small detail at Acts 27:9, where Luke dates the sailing season by saying that the Fast was already over, meaning the Day of Atonement — evidence that he expected his readers to locate a month in the year by naming a fast.
Paul lists fasting among the ordinary contents of his own life twice, in the two passages where he catalogues what being an apostle consists of: in stripes, in imprisonments, in tumults, in labours, in sleeplessness, in fastings (2 Corinthians 6:5), and in weariness and toil, in sleeplessness often, in hunger and thirst, in fastings often, in cold and nakedness (11:27). Honesty requires a caveat: commentators disagree over whether the word in 11:27 means voluntary fasting or involuntary hunger, since Paul's subject there is hardship. The best evidence against the involuntary reading is in the verse itself, which names hunger and thirst separately and then adds fastings often, and the lists in both places mix afflictions inflicted on him with disciplines he undertook. Alongside them stands 1 Corinthians 9:27, where he says he disciplines his body and brings it into subjection lest he himself should become disqualified — not about food specifically, but the ascetic principle in his own words, and in a letter.
The Old Testament, and the one place the rule comes from
The Old Testament evidence is abundant and ought to be cited precisely rather than waved at. Moses fasts forty days on the mountain without bread or water (Exodus 34:28). Elijah walks forty days to Horeb (3 Kingdoms 19:8 [1 Kings 19:8]). David fasts and lies on the ground for his dying child (2 Kingdoms 12:16 [2 Samuel 12:16]). The Law appoints an annual day on which the people afflict their souls (Leviticus 16:29–31), and Zechariah 8:19 names four established fasts by the months in which they fell. Esther tells Mordecai to gather the Jews of Susa and fast for her, neither eating nor drinking three days, night or day, before she goes in to the king unsummoned (Esther 4:16). Nineveh fasts under the king's decree, in sackcloth, man and beast, and the text is careful about what God actually saw: Then God saw their works, that they turned from their evil way (Jonah 3:10). Joel gives the classic summons to a corporate fast — turn to Me with all your heart, with fasting, with weeping and with mourning, and rend your heart and not your garments, consecrate a fast, call a sacred assembly (Joel 2:12–15) — which is the biblical warrant for a fast that a whole people keeps together on appointed days rather than a fast each person invents.
But the closest biblical analogue to the actual Orthodox rule is Daniel, and it is not quoted nearly often enough. In those days I, Daniel, was mourning three full weeks. I ate no pleasant food, no meat or wine came into my mouth, nor did I anoint myself at all (Daniel 10:2–3). Read what that describes. It is not a total fast; he ate. It is not one day; it is three weeks. It is defined entirely by what was removed, and the three things removed are flesh, wine and oil. That is the Orthodox fast, item for item, in the Old Testament, kept for a period of weeks by a prophet, with no suggestion that he was doing anything eccentric. The earlier episode in Babylon is the same in principle, where Daniel and his companions ask for vegetables and water instead of the king's provision and are visibly the better for it (Daniel 1:8–16). Whatever one concludes about the authority of the Church's calendar, the shape of the thing on the calendar is not an invention of Byzantine monks. It is Daniel's.
The fast God refuses
The strongest thing that can be said about Orthodox fasting is also the thing most damaging to it, and the Church did not leave it to critics to say. On the weekdays of Great Lent the Old Testament is read in course at the services — Genesis and Proverbs at Vespers, Isaiah at the Sixth Hour — and nearly the whole of Isaiah goes by across the weeks. Which means that chapter 58 is read aloud, annually, to a congregation in the middle of the fast, by people who are keeping it, at the point in the season when self-congratulation has had a month to set.
The chapter opens with the people's grievance, quoted back at them: why have we fasted, and You have not seen? Why have we afflicted our souls, and You take no notice? The answer is that on the day of their fast they pursue their own business and press their workers, that they fast for strife and contention and to strike with the fist of wickedness, and that a fast like that will not make a voice heard on high. Then comes the definition, and it is not about food at all.
Is this not the fast that I have chosen: to loose the bonds of wickedness, to undo the heavy burdens, to let the oppressed go free, and that you break every yoke? Is it not to share your bread with the hungry, and bring to your house the poor who are cast out; when you see the naked, that you cover him, and not hide yourself from your own flesh?Isaiah 58:6–7
The Orthodox Study Bible's Old Testament follows the St Athanasius Academy Septuagint, whose rendering of these verses differs in wording from the version most Protestant readers will recognise — it speaks, for instance, of tearing up unjust contracts and of untying the knots of forced agreements. The force is identical and in places sharper. The wording given above is the one a Protestant reader is likeliest to know, and the reference is the same in both.
Only after that do the promises come: light breaking forth like the morning, healing springing up speedily, and the Lord answering, Here I am. The structure of the chapter puts mercy and justice before the promises and treats the dietary observance as the thing under judgement rather than the thing being rewarded. And the Church's own arrangement of the season says the same. The Gospel of the last day on which meat is eaten is Matthew 25, which sorts the nations on who fed the hungry; the Gospel of the last day of dairy is Matthew 6, on secrecy and forgiveness; the parable that opens the whole season is the one in which the man who fasts twice a week goes home condemned.
The test Isaiah sets is not whether the plate was clean. It is whether the poor ate. An Orthodox Christian who keeps the whole rule for seven weeks without having fed anybody has, by the judgement of the chapter his own church read aloud to him while he was doing it, kept nothing at all. This is not a Protestant objection that Orthodoxy has to survive. It is the Orthodox lectionary, and a tradition anxious to protect a dietary rule from criticism would not read that chapter in the middle of the rule, every year, out loud.