#1 WESTMINSTER CONFESSION OF FAITH
CH 21 – Of Religious Worship, and the Sabbath Day
WCF 21.5: The reading of the Scriptures with godly fear; the sound preaching, and conscionable hearing of the Word, in obedience unto God with understanding, faith, and reverence; singing of psalms with grace in the heart; as, also, the due administration and worthy receiving of the sacraments instituted by Christ; are all parts of the ordinary religious worship of God: besides religious oaths, and vows, solemn fastings, and thanksgivings upon special occasion; which are, in their several times and seasons, to be used in an holy and religious manner.
 Joel 2:12 Therefore also now, saith the Lord, turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning.
Esther 4:16 Go, gather together all the Jews that are present in Shushan, and fast ye for me, and neither eat nor drink three days, night or day: I also and my maidens will fast likewise; and so will I go in unto the king, which is not according to the law: and if I perish, I perish.
Matt 9:15 And Jesus said unto them, Can the children of the bridechamber mourn, as long as the bridegroom is with them? but the days will come, when the bridegroom shall be taken from them, and then shall they fast.
1 Cor 7:5 Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
Esther 9:22 As the days wherein the Jews rested from their enemies, and the month which was turned unto them from sorrow to joy, and from mourning into a good day: that they should make them days of feasting and joy, and of sending portions one to another, and gifts to the poor.
#2 WESTMINSTER DIRECTORY FOR THE PUBLIC WORSHIP OF GOD
Concerning Publick Solemn Fasting
WHEN some great and notable judgments are either inflicted upon a people, or apparently imminent, or by some extraordinary provocations notoriously deserved; as also when some special blessing is to be sought and obtained, publick solemn fasting (which is to continue the whole day) is a duty that God expecteth from that nation or people.
A religious fast requires total abstinence, not only from all food, (unless bodily weakness do manifestly disable from holding out till the fast be ended, in which case somewhat may be taken, yet very sparingly, to support nature, when ready to faint,) but also from all worldly labour, discourses, and thoughts, and from all bodily delights, and such like, (although at other times lawful,) rich apparel, ornaments, and such like, during the fast; and much more from whatever is in the nature or use scandalous and offensive, as gaudish attire, lascivious habits and gestures, and other vanities of either sex; which .i.we; recommend to all ministers, in their places, diligently and zealously to reprove, as at other times, so especially at a fast, without respect of persons, as there shall be occasion.
Before the publick meeting, each family and person apart are privately to use all religious care to prepare their hearts to such a solemn work, and to be early at the congregation.
So large a portion of the day as conveniently may be, is to be spent in publick reading and preaching of the word, with singing of psalms, fit to quicken affections suitable to such a duty: but especially in prayer, to this or the like effect:
“Giving glory to the great Majesty of God, the Creator, Preserver, and supreme Ruler of all the world, the better to affect us thereby with an holy reverence and awe of him; acknowledging his manifold, great, and tender mercies, especially to the church and nation, the more effectually to soften and abase our hearts before him; humbly confessing of sins of all sorts, with their several aggravations; justifying God’s righteous judgments, as being far less than our sins do deserve; yet humbly and earnestly imploring his mercy and grace for ourselves, the church and nation, for our king, and all in authority, and for all others for whom we are bound to pray, (according as the present exigent requireth,) with more special importunity and enlargement than at other times; applying by faith the promises and goodness of God for pardon, help, and deliverance from the evils felt, feared, or deserved; and for obtaining the blessings which we need and expect; together with a giving up of ourselves wholly and for ever unto the Lord.”
In all these, the ministers, who are the mouths of the people unto God, ought so to speak from their hearts, upon serious and thorough premeditation of them, that both themselves and their people may be much affected, and even melted thereby, especially with sorrow for their sins; that it may be indeed a day of deep humiliation and afflicting of the soul.
Special choice is to be made of such scriptures to be read, and of such tests for preaching, as may best work the hearts of the hearers to the special business of the day, and most dispose them to humiliation and repentance: insisting most on those particulars which each minister’s observation and experience tells him are most conducing to the edification and reformation of that congregation to which he preacheth.
Before the close of the publick duties, the minister is, in his own and the people’s name, to engage his and their hearts to be the Lord’s, with professed purpose and resolution to reform whatever is amiss among them, and more particularly such sins as they have been more remarkably guilty of; and to draw near unto God, and to walk more closely and faithfully with him in new obedience, than ever before.
He is also to admonish the people, with all importunity, that the work of that day doth not end with the publick duties of it, but that they are so to improve the remainder of the day, and of their whole life, in reinforcing upon themselves and their families in private all those godly affections and resolutions which they professed in publick, as that they may be settled in their hearts for ever, and themselves may more sensibly find that God hath smelt a sweet savour in Christ from their performances, and is pacified towards them, by answers of grace, in pardoning of sin, in removing of judgments, in averting or preventing of plagues, and in conferring of blessings, suitable to the conditions and prayers of his people, by Jesus Christ.
Besides solemn and general fasts enjoined by authority, we judge that, at other times, congregations may keep days of fasting, as divine providence shall administer unto them special occasion; and also that families may do the same, so it be not on days wherein the congregation to which they do belong is to meet for fasting, or other publick duties of worship.
Concerning the Observation of Days of Publick Thanksgiving
WHEN any such day is to be kept, let notice be given of it, and of the occasion thereof, some convenient time before, that the people may the better prepare themselves thereunto.
The day being come, and the congregation (after private preparations) being assembled, the minister is to begin with a word of exhortation, to stir up the people to the duty for which they are met, and with a short prayer for God’s assistance and blessing, (as at other conventions for publick worship,) according to the particular occasion of their meeting.
Let him then make some pithy narration of the deliverance obtained, or mercy received, or of whatever hath occasioned that assembling of the congregation, that all may better understand it, or be minded of it, and more affected with it.
And, because singing of psalms is of all other the most proper ordinance for expressing of joy and thanksgiving, let some pertinent psalm or psalms be sung for that purpose, before or after the reading of some portion of the word suitable to the present business.
Then let the minister, who is to preach, proceed to further exhortation and prayer before his sermon, with special reference to the present work: after which, let him preach upon some text of Scripture pertinent to the occasion.
The sermon ended, let him not only pray, as at other times after preaching is directed, with remembrance of the necessities of the Church, King, and State, (if before the sermon they were omitted,) but enlarge himself in due and solemn thanksgiving for former mercies and deliverances; but more especially for that which at the present calls them together to give thanks: with humble petition for the continuance and renewing of God’s wonted mercies, as need shall be, and for sanctifying grace to make a right use thereof. And so, having sung another psalm, suitable to the mercy, let him dismiss the congregation with a blessing, that they may have some convenient time for their repast and refreshing.
But the minister (before their dismission) is solemnly to admonish them to beware of all excess and riot, tending to gluttony or drunkenness, and much more of these sins themselves, in their eating and refreshing; and to take care that their mirth and rejoicing be not carnal, but spiritual, which may make God’s praise to be glorious, and themselves humble and sober; and that both their feeding and rejoicing may render them more cheerful and enlarged, further to celebrate his praises in the midst of the congregation, when they return unto it in the remaining part of that day.
When the congregation shall be again assembled, the like course in praying, reading, preaching, singing of psalms, and offering up of more praise and thanksgiving, that is before directed for the morning, is to be renewed and continued, so far as the time will give leave.
At one or both of the publick meetings that day, a collection is to be made for the poor, (and in the like manner upon the day of publick humiliation,) that their loins may bless us, and rejoice the more with us. And the people are to be exhorted, at the end of the latter meeting, to spend the residue of that day in holy duties, and testifications of Christian love and charity one towards another, and of rejoicing more and more in the Lord; as becometh those who make the joy of the Lord their strength.
…What the US congress had in mind? … I don’t think so!