The 144000 are identified as the firstfruits to God. having the Father’s name written on their foreheads who are redeemed from the earth. They are not defiled with women and follow the Lamb wherever He goes. No deceit was found in their mouth and they are without fault before the throne of God.

(Lev 23:34,39-40) “Speak to the children of Israel, saying: ‘The fifteenth day of this seventh month [shall be] the Feast of Tabernacles [for] seven days to the LORD. ‘ Also on the fifteenth day of the seventh month, when you have gathered in the fruit of the land, you shall keep the feast of the LORD [for] seven days; on the first day [there shall be] a sabbath-[rest,] and on the eighth day a sabbath-[rest.] ‘And you shall take for yourselves on the first day the fruit of beautiful trees, branches of palm trees, the boughs of leafy trees, and willows of the brook; and you shall rejoice before the LORD your God for seven days.  

(Deut 16:13) ” You shall observe the Feast of Tabernacles seven days, when you have gathered from your threshing floor and from your winepress.

The 144000 are sealed by God for the fruits on the first day of the feast, which Christ will take for Himself and they will go wherever He goes.

1st Angel: Everlasting Gospel

(Rev 14:6-7) Then I saw another angel flying in the midst of heaven, having the everlasting gospel to preach to those who dwell on the earth–to every nation, tribe, tongue, and people– saying with a loud voice, “Fear God and give glory to Him, for the hour of His judgment has come; and worship Him who made heaven and earth, the sea and springs of water.”

Who is God? The creator of heaven and earth, the sea and the springs of water.
What must we do? Fear God, give glory to Him, worship God.
Why we must do? His judgment has come

Jesus Himself said this event would happen.

(Matt 24:14) “And this gospel of the kingdom will be preached in all the world as a witness to all the nations, and then the end will come.

Gospel is not yet preached to all nations and still several are unreachable mainly due to fear of persecution. Based on the revelation passage, it seems gospel will not be preached to all the world even up to this point in future and finally an angel will preach to all.

(Gal 1:8) But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed. 

(1Pet 1:12) To them it was revealed that, not to themselves, but to us they were ministering the things which now have been reported to you through those who have preached the gospel to you by the Holy Spirit sent from heaven–things which angels desire to look into.

Paul in his letter to Galatians says that any angel preaching another gospel will be cursed. Peter also mentions about angels that they desire to look into what the gospel is.

2nd Angel: Babylon is Fallen

(Rev 14:8) And another angel followed, saying, “Babylon is fallen, is fallen, that great city, because she has made all nations drink of the wine of the wrath of her fornication.”

It is important to understand this is the first mention of the mystery Babylon. If you notice the word “that”, it seems as though the reader has already read and knew what Babylon is. However, translations like Young’s Literal Translation simply translates “the great city”. Spiritual fornication refers to worshiping other gods. She forced all the nations to follow a false god. Mystery Babylon is identified as Mecca in later chapters.

3rd Angel: Wrath of God

(Rev 14:9-13) Then a third angel followed them, saying with a loud voice, “If anyone worships the beast and his image, and receives his mark on his forehead or on his hand, “he himself shall also drink of the wine of the wrath of God, which is poured out full strength into the cup of His indignation. He shall be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb. “And the smoke of their torment ascends forever and ever; and they have no rest day or night, who worship the beast and his image, and whoever receives the mark of his name.” Here is the patience of the saints; here are those who keep the commandments of God and the faith of Jesus. Then I heard a voice from heaven saying to me, “Write: ‘Blessed are the dead who die in the Lord from now on.’ ” “Yes,” says the Spirit, “that they may rest from their labors, and their works follow them.”

A warning is given to all of God’s people about the coming judgment to the beast and it’s worshipers prior to anyone receiving the mark of the beast, even before it happens. It refers to the well informed nature of the people before they receive the mark of the beast. Blessed are all who will die in the Lord from that point in future for it is the beginning of the great tribulation, and Christ will give them rest.

(Matt 11:28) “Come to Me, all you who labor and are heavy laden, and I will give you rest.

While all those who received the mark were warned about being cast into lake of fire and brimstone, only the beast and the false prophet were cast into the lake of fire and brimstone during the Christ’s second coming which is before the millennium reign of Christ, but the rest are cast during the white throne judgment which is after the millennium reign of Christ.

(Rev 19:20-21) Then the beast was captured, and with him the false prophet who worked signs in his presence, by which he deceived those who received the mark of the beast and those who worshiped his image. These two were cast alive into the lake of fire burning with brimstone. And the rest were killed with the sword which proceeded from the mouth of Him who sat on the horse. And all the birds were filled with their flesh. 

(Rev 20:15) And anyone not found written in the Book of Life was cast into the lake of fire.

Final Harvest

(Rev 14:14-20) Then I looked, and behold, a white cloud, and on the cloud sat One like the Son of Man, having on His head a golden crown, and in His hand a sharp sickle. And another angel came out of the temple, crying with a loud voice to Him who sat on the cloud, “Thrust in Your sickle and reap, for the time has come for You to reap, for the harvest of the earth is ripe.” So He who sat on the cloud thrust in His sickle on the earth, and the earth was reaped. Then another angel came out of the temple which is in heaven, he also having a sharp sickle. And another angel came out from the altar, who had power over fire, and he cried with a loud cry to him who had the sharp sickle, saying, “Thrust in your sharp sickle and gather the clusters of the vine of the earth, for her grapes are fully ripe.” So the angel thrust his sickle into the earth and gathered the vine of the earth, and threw it into the great winepress of the wrath of God. And the winepress was trampled outside the city, and blood came out of the winepress, up to the horses’ bridles, for one thousand six hundred furlongs.

The great harvest of the Lord described here also refers to the feast of the tabernacles or in-gathering. Both John the baptist and also Christ mentions this very event.

(Matt 3:11-12) “I indeed baptize you with water unto repentance, but He who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire. “His winnowing fan is in His hand, and He will thoroughly clean out His threshing floor, and gather His wheat into the barn; but He will burn up the chaff with unquenchable fire.”

John refers wheat to righteous and holy people and chaff refers to those who practice lawlessness. God will gather the righteous and holy people into His barn while the chaff will be burnt with unquenchable fire.

(Matt 13:24-30) Another parable He put forth to them, saying: “The kingdom of heaven is like a man who sowed good seed in his field; “but while men slept, his enemy came and sowed tares among the wheat and went his way. “But when the grain had sprouted and produced a crop, then the tares also appeared. “So the servants of the owner came and said to him, ‘Sir, did you not sow good seed in your field? How then does it have tares?’  “He said to them, ‘An enemy has done this.’ The servants said to him, ‘Do you want us then to go and gather them up?’ “But he said, ‘No, lest while you gather up the tares you also uproot the wheat with them. ‘Let both grow together until the harvest, and at the time of harvest I will say to the reapers, “First gather together the tares and bind them in bundles to burn them, but gather the wheat into my barn.” ’ ”

Similar to John’s preaching, Jesus also said the wheat will be gathered into the barn and the tares will be gathered and burnt. Jesus is speaking about the final harvest during his second coming.