The prophecy which commences this chapter occupies the first ten verses. That it relates to Babylon is apparent from Isaiah 21:2, Isaiah 21:9. The object is to foretell the destruction of that city by the Medes and Persians, and the design is the same as in the more extended and minute description of the same event in Isaiah. 13; 14: Whether it was delivered at the same, or at another time, cannot be determined from the prophecy. The purpose, however, of the prophecy is the same as there - to give consolation to the Jews who should be carried captive to that city; to assure them that Babylon would be destroyed, and that they would be delivered from their long and severe bondage. This is indicated in a brief and graphic manner in Isaiah 21:10.
This oracle, or ode, is one of singular beauty. It is distinguished for its brevity, energy, and force, for the variety and the rapidity of the action, and for the vivid manner in which the events are made to pass before the mind. It is the language of strong excitement and of alarm; language that expresses rapid and important movements; and language appropriate to great vigor of conception and sublimity in description. In the oracle the prophet supposes himself in Babylon, and the events which are described are made to pass rapidly in vision (see the Introduction, Section 7, 4) before him. He first sees Isaiah 21:1 the dreadful storm coming at a distance (the hostile armies), approaching like a whirlwind and threatening destruction to everything in its way. He then Isaiah 21:2 hears God's direction to the invading armies; represents himself as made acquainted with the design of the vision, and hears the command of God to Elam (Persia) and Media to go up and commence the siege.
Regarding himself as among the exiles in the midst of Babylon, he Isaiah 21:3-4 describes himself as deeply affected in view of this sudden invasion, and of the calamities that were coming upon Babylon. In Isaiah 21:5, he describes the state of the Babylonians. They are represented, first as preparing the table, making ready for feasting and revelry, setting the watch on the watch-tower, and giving themselves up to dissipation; and secondly, as suddenly alarmed, and summoned to prepare for war. He then (Isaiah 21:6-9 declares the way in which the princes of Babylon would be roused from their revelry. But it is described in a very remarkable manner. He does not "narrate" the events, but he represents himself as directed to appoint a watchman Isaiah 21:6 to announce what he should see. That watchman Isaiah 21:7 sees two chariots - representing two nations coming rapidly onward to execute the orders of God. So rapid is their approach, so terrible their march, that the watchman cries out Isaiah 21:9 that Babylon is fallen, and will be inevitably destroyed. The prophecy is then closed Isaiah 21:10 by an address to the afflicted Jews whom God had 'threshed,' or punished by sending them captive to Babylon, and with the declaration that this was intended by the Lord of hosts to be declared unto them. The whole design of the prophecy, therefore, is to console them, and to repeat the assurance given in Isaiah. 13; 14, that Babylon would be destroyed, and that they would be delivered from bondage.

Prediction of the taking of Babylon by the Medes and Persians at the time of a great festival, Isaiah 21:1-9. Short application of the prophecy to the Jews, partly in the person of God, and partly in his own, Isaiah 21:10. Obscure prophecy respecting Dumah, Isaiah 21:11, Isaiah 21:12. Prophecy concerning the Arabians to be fulfilled in a very short time after its delivery, Isaiah 21:13-17.
The first ten verses of this chapter contain a prediction of the taking of Babylon by the Medes and Persians. It is a passage singular in its kind for its brevity and force, for the variety and rapidity of the movements, and for the strength and energy of coloring with which the action and event are painted. It opens with the prophet's seeing at a distance the dreadful storm that is gathering and ready to burst upon Babylon. The event is intimated in general terms, and God's orders are issued to the Persians and Medes to set forth upon the expedition which he has given them in charge. Upon this the prophet enters into the midst of the action; and in the person of Babylon expresses, in the strongest terms, the astonishment and horror that seizes her on the sudden surprise of the city at the very season dedicated to pleasure and festivity, Isaiah 21:3, Isaiah 21:4. Then, in his own person, describes the situation of things there, the security of the Babylonians, and in the midst of their feasting the sudden alarm of war, Isaiah 21:5. The event is then declared in a very singular manner. God orders the prophet to set a watchman to look out, and to report what he sees; he sees two companies marching onward, representing by their appearance the two nations that were to execute God's orders, who declare that Babylon is fallen, Isaiah 21:6-9.
But what is this to the prophet, and to the Jews, the object of his ministry? The application, the end, and design of the prophecy are admirably given in a short, expressive address to the Jews, partly in the person of God, partly in that of the prophet: "O my threshing" "O my people, whom for your punishment I shall make subject to the Babylonians, to try and to prove you, and to separate the chaff from the corn, the bad from the good, among you; hear this for your consolation: your punishment, your slavery, and oppression will have an end in the destruction of your oppressors." - L.

INTRODUCTION TO ISAIAH 21
This chapter contains prophecies against Babylon, Idumea, and Arabia. The prophecy against Babylon is called "the burden of the desert of the sea"; whose enemies are described by the fierce manner of their coming, and by the land from whence they came, Isaiah 21:1 which vision being declared to the prophet, is called a grievous one; what made it so was treachery among themselves; and the Medes and Persians are invited to besiege them, Isaiah 21:2 their terror and distress upon it are represented by the pains of a woman in travail, whom the prophet personates, Isaiah 21:3 and by the methods they took to defend themselves, to which they were alarmed, when in the greatest security and jollity, Isaiah 21:5 all which is illustrated by the vision of the watchman, who saw the Medes and Persians on the march, signified by a chariot and a couple of horsemen, who declares the fall of Babylon, and the destruction of its gods, Isaiah 21:6 which would issue in the good and comfort of the church and people of God, Isaiah 21:10 then follows the prophecy against Idumea, which consists of a question put to the watchman, and his answer to it; to which an exhortation is added, Isaiah 21:11 and the chapter concludes with another prophecy against Arabia: the calamities threatened are lodging in a forest, thirst, famine, and fleeing from the sword Isaiah 21:13, and the time is fixed when all this should be, by which their glory would fail, and the number of their archers and mighty men be lessened; for the confirmation of which the divine testimony is annexed, Isaiah 21:16.

(Isaiah 21:1-10) The taking of Babylon.
(Isaiah 21:11, Isaiah 21:12) Of the Edomites.
(Isaiah 21:13-17) Of the Arabs.

The Oracle Concerning the Desert of the Sea (Babylon) - Isaiah 21:1-10
Ewald pronounces this and other headings to be the glosses of ancient readers (proph. i. 56, 57). Even Vitringa at first attributed it to the collectors, but he afterwards saw that this was inadmissible. In fact, it is hardly possible to understand how the expression "desert of the sea" (midbar-yâm) could have been taken from the prophecy itself; for yâm cannot signify the south (as though synonymous with negeb), but is invariably applied to the west, whilst there is nothing about a sea in the prophecy. The heading, therefore, is a peculiar one; and this Knobel admits, though he nevertheless adheres to the opinion that it sprang from a later hand. But why? According to modern critics, the hand by which the whole massa was written was certainly quite late enough. From Koppe to Knobel they are almost unanimous in asserting that it emanated from a prophet who lived at the end of the Babylonian captivity. And Meier asserts with dictatorial brevity, that no further proof is needed that Isaiah was not the author. But assuming, what indeed seems impossible to modern critics - namely, that a prophet's insight into futurity might stretch over hundreds of years - the massa contains within itself and round about itself the strongest proofs of its genuineness. Within itself: for both the thoughts themselves, and the manner in which they are expressed, are so thoroughly Isaiah's, even in the most minute points, that it is impossible to conceive of any prophecy in a form more truly his own. And round about itself: inasmuch as the four massa's (Isaiah 21:1-10, Isaiah 21:11-12, Isaiah 21:13-17; 22), are so intertwined the one with the other as to form a tetralogy, not only through their emblematical titles (compare Isaiah 30:6) and their visionary bearing, but also in many ways through the contexts themselves. Thus the designation of the prophet as a "watchman" is common to the first and second massa's; and in the fourth, Jerusalem is called the valley of vision, because the watch-tower was there, from which the prophet surveyed the future fate of Babylon, Edom, and Arabia. And just as in the first, Elam and Madai march against Babylon; so in the fourth (Isaiah 22:6) Kir and Elam march against Jerusalem. The form of expression is also strikingly similar in both instances (compare Isaiah 22:6-7, with Isaiah 21:7). Is it then possible that the first portion of the tetralogy should be spurious, and the other three genuine? We come to the same conclusion in this instance as we did at Isaiah 13:1.; and that, most truly, neither from a needless apologetical interest, nor from forced traditional prejudice. Just as the massâ Bâbel rests upon a prophecy against Asshur, which forms, as it were, a pedestal to it, and cannot be supposed to have been placed there by any one but Isaiah himself; so that massa midbar-yâm rests, as it were, upon the pillars of its genuineness, and announces itself velut de tripode as Isaiah's. This also applies to the heading. We have already noticed, in connection with Isaiah 15:1, how closely the headings fit in to the prophecies themselves. Isaiah is fond of symbolical names (Isaiah 29:1; Isaiah 30:7). And midbar-yâm (desert of the sea) is a name of this kind applied to Babylon and the neighbourhood. The continent on which Babylon stood was a midbâr, a great plain running to the south into Arabia deserta; and so intersected by the Euphrates as well as by marshes and lakes, that it floated, as it were, in the sea. The low-lying land on the Lower Euphrates had been wrested, as it were, from the sea; for before Semiramis constructed the dams, the Euphrates used to overflow the whole just like a sea (πελαγίζειν, Herod. i. 184). Abydenus even says, that at first the whole of it was covered with water, and was called thalassa (Euseb. praep. ix. 41). We may learn from Isaiah 14:23, why it was that the prophet made use of this symbolical name. The origin and natural features of Babylon are made into ominous prognostics of its ultimate fate. The true interpretation is found in Jeremiah (Jeremiah 51:13; Jeremiah 50:38), who was acquainted with this oracle.