"A prophecy against the Desert by the Sea: Like whirlwinds sweeping through the southland, an invader comes from the desert, from a land of terror." NIV translation
The "Desert by the Sea" speaks of opposites and what is commonly called a mirage. A mirage is something that appears to be real but is not and, in nature, it is caused by the refraction of light by heated air. The most common example is of a sheet of water appearing to be in the desert. In this case, the phrase is being used to identify the nation of Babylon. The city appeared to be wonderful but, in fact, was full of death due to the rampant idolatry.
"A dire vision has been shown to me: The traitor betrays, the looter takes loot. Elam, attack! Media, lay siege! I will bring to an end all the groaning she caused." NIV translation
Elam refers to Persia as they became a part of the Persian army. This verse corresponds to the visions of Daniel and the defeat of the Babylonians at the hands of the Medo-Persian empire which happened in 539 B.C. The Babylonians had appeared to be unbeatable in their fortress but their strength was proved to be a mirage when the fortress fell in a single night.
Isaiah 21:3 & 4
"At this my body is racked with pain, pangs seize me, like those of a woman in labor; I am staggered by what I hear, I am bewildered by what I see. My heart falters, fear makes me tremble; the twilight I longed for has become a horror to me." NIV translation
We see that this vision of judgment is terrible as it physically shakes the prophet to his core. Isaiah had longed for God to judge Babylon but, when he saw how terrible it was, it really troubled him. That is a reminder to us that we, as Christians, look forward to the judgment and long to see the return of Christ but it will be horrible for those that have rejected Him.
"They set the tables, they spread the rugs, they eat, they drink! Get up, you officers, oil the shields!" NIV translation
This verse predicts the fact that the Babylonians would be having a giant party as their city was being compromised. At this party, they even took articles that they had captured in Jerusalem and desecrated them as they used them to get drunk. While they were having this party, the Medes entered the city and defeated them and Darius the Mede took over their kingdom (see Daniel 5). Instead of preparing for the battle that they knew was coming, the leaders of the Babylonians were involved in the party. God had used them as an instrument of judgment but they were now judged themselves.
Isaiah 21:6 & 7
"This is what the Lord says to me: 'Go, post a lookout and have him report what he sees. When he sees chariots with teams of horses, riders on donkeys or riders on camels, let him be alert, fully alert.'" NIV translation
God assures Isaiah that the Babylonians will fall just as He said. He went so far as to say that the people should post a watchman to keep an eye out for the news. This is a reminder to us as well that, when God says that something will happen, we can watch out because it will happen.
"And the lookout shouted, 'Day after day, my Lord, I stand on the watchtower; every night I stay at my post. Look, here comes a man in a chariot with a team of horses. And he gives back the answer: "Babylon has fallen, has fallen! All the images of its gods lie shattered on the ground!"' My people who are crushed on the threshing floor, I tell you what I have heard from the Lord Almighty, from the God of Israel." NIV translation
Isaiah reassures the people of what God has shown him and the fact that those who were oppressing them would be judged.
The same type of assurance is for us, as Christians, today. Though we face discrimination many times as well as outright persecution in some areas, in the end God will pronounce judgment on those who cause it.
Isaiah 21:11 & 12
"A prophecy against Dumah: Someone calls to me from Seir, 'Watchman, what is left of the night? Watchman, what is left of the night?' The watchman replies, 'Morning is coming, but also the night. If you would ask, then ask; and come back yet again.'" NIV translation
Dumah means silence and it is a symbolic word as it is Edom with the "E" removed and Seir means rough or hairy.
This burden is for the descendants of Esau who lived in the area south of the Dead Sea. A watchman was responsible for watching out for danger and alerting a city and we see that Isaiah assumes this title. The people ask the watchman how much longer it will be dark and his reply is that light is coming for some but darkness for others.
This is a reminder to us, as Christians, that the imminent return of Christ will be a wonderful time for us but it will be a time of great darkness and trouble for others. Just as Isaiah assumed the role of watchman with its responsibility, we, too, have the role for the world today. We must warn the people that morning is coming for us but darkness night for those who do not know Jesus Christ.
"A prophecy against Arabia: You caravan of Dedanites, who camp in the thickets of Arabia, bring water for the thirsty; you who live in Tema, bring food for the fugitives. They flee from the sword, from the drawn sword, from the bent bow and from the heat of battle." NIV translation
The Dedanites lived in the northern part of what is known as Saudi Arabia which was just south of Babylon. They used basic weapons such as the bow but were faced with swords and shields of the Assyrians.
Isaiah 21:16 & 17
"This is what the Lord says to me: 'Within one year, as a servant bound by contract would count it, all of the splendor of Kedar will come to an end. The survivors of the archers, the warriors of Kedar, will be few.' The Lord, the God of Israel, has spoken." NIV translation
Kedar was the home of nomadic tribes in the Arabian desert and Isaiah warns them that within one year they would be conquered. He says that few will survive and that it is decreed by God.