Christ now preaches a sermon. Did the Worship of the Shalems include a sermon, following the bread and wine? Christ, having just come from behind the veil as high priest / Melchizedek / Lord and delivered the bread of his body and the wine of his blood, takes as his text Isaiah. Apparently, all of Isaiah. "When the words of Isaiah should be fulfilled" begins his sermon, which presumably means that he and the multitude both saw his administering the shalem feast to them as a fulfillment of Isaiah.
We should read Isaiah with that in mind.