Feasts, festivals, banquets, and wedding suppers abound in the Bible, and with good reason: meal fellowship represents community of the closest kind, especially perhaps in tribal cultures (then and now); and feasts give rise to abundance, even in times of distress.
When people celebrate, they are often able to share in surprising ways, welcoming others to the table. More than once, African friends gave me the equivalent of the widow's mite, sharing graciously out of their poverty to celebrate our time together.
So, what of the banquet in our text? It becomes paradigmatic -- a model or sign of all the feasts God has in store for us -- precisely because of the uncertainty of its context in the book of Isaiah. Most scholars see Isaiah 24-27 (sometimes called Isaiah's "little apocalypse") as a unit hard to pin down to a particular time and place. The chapters announce the hope and judgment that will come "on that day" (seven times in four chapters) -- and, as with all "apocalyptic" texts, attempts to determine the day and the hour will not only fail, they will get in the way of hearing the message of the text to its original hearers and to us.
Like most prophetic material, the texts are poetry, and the preacher/exegete must allow them to be just that: signs, images, metaphors, hints, and exercises in playfulness and imagination that let us in on what God is doing without requiring too exact determinations of when and where. (If, for no other reason, than that such determination will make the texts inapplicable to some times and places by claiming them too precisely for another.)
Though Isaiah's feast lacks a clear historical context, it does have a literary context, and that matters for its meaning. If we read the text given in the pericope, we have fierce judgment on "the ruthless" (three times in verses 1-5), followed by the banquet of abundance for "all peoples" (verses 6-9).
So, law and gospel? But the text continues, even if the pericope does not, to pronounce judgment again (ugly judgment) on the "Moabites" (verses 10b-12).
So, law, gospel, law? We should not try to turn this into an exercise in the "proper relationship of law and gospel," since the text does not mean to do that (indeed, it knows nothing of such a discussion), but it does provide a judgment/promise/judgment chiasm, where we see God's glorious promise "surrounded" by the judgment of the wicked.
Those wicked just won't seem to go away -- not here, not in Psalm 23 (another banquet "in the presence of my enemies"), and not in Matthew's wedding banquet, where the guest without a garment (without demonstrating the new life that should come from an encounter with divine abundance?) is unceremoniously dismissed. God's parties (even if timeless) happen in a real world, where real people do wicked or stupid things and thus, in effect, vote themselves "off the island."
I would certainly include verse 10a in the sermon text. It closes the section begun in verse 6 (note the parenthetical repetition of "on this mountain" in verses 6 and 10a), and it provides a theme that ties together the judgment and the promise of the chapter: "For the hand of the Lord will rest on this mountain."
Is that a good thing or a bad thing? Yes! A quick concordance check will demonstrate that the "hand of the Lord" -- that symbol of God's active power and presence -- is both positive and negative in the Bible (actually, more often the latter). It is the power that turns back the Egyptians (Exodus 9:3), that turns against a rebellious Israel (1 Samuel 12:15), that symbolizes the raw power of whatever God is up to (unfairly?) in Job (Job 12:9-10); but it is also the symbol of God's "powerful" mercy (2 Samuel 24:14), and it will guide John the Baptist on his mission (Luke 1:66). Hebrews is right that "it is a fearful thing to fall into the hands of the living God" (Hebrews 10:31); yet, so is Matthew with his assurance that the touch of Jesus' hand will give life (Matthew 9:18).
That is the literary/theological context for Isaiah's banquet, and it matters. Not that God is capricious ("Is the old man in a good mood today?"), but that the good world that God desires for "all peoples" means that those who behave ruthlessly to others and those who, like Moab, refuse and despise hospitality to others, will find themselves excluded (their own choice, actually).
Ah, but in the middle of that troubled world, what a banquet! Perhaps only the poor can truly appreciate the feast (just as only the downtrodden can truly appreciate the importance of defeating the oppressors). For us (most of us, anyway), who are more or less affluent and safe, God's" judgment" becomes a problematic abstraction, and the glorious banquet ("fat things full of marrow" and "wine on the lees" RSV) becomes a terrifying threat of obesity and addiction.
Enjoying the fat, the rich marrow, and the abundant wine is beyond-their-wildest-imagination promise for those who rarely see such things. The same things can become repugnant to those who daily have the problem of too much rather than too little. To appreciate the text, we need to recognize our need -- always a reality, no matter our relative wealth by the standards of the world. It will be up to the preacher to translate the text into promise for a particular congregation (which, to be sure, may include both the haves and the have nots).
For rich and poor, death remains a problem, of course, so the promise of God's defeat of that final enemy will apply to all. This promise, too, is not merely about the afterlife (though it will move in that direction in the biblical tradition), but about the "shroud" that covers us always -- the fear, the pain, the little deaths that get in the way of the abundant life God desires for us.
The lack of historical context does not make this text "timeless" in the sense that it is for an unknown future, but "timeless" as in "timely" for every generation. That is what I mean by "paradigmatic." This is what God is up to. This is who God is. This is what God wants for us. A properly textual sermon on these verses will proclaim this God and this promise today -- for "all nations."