The source of Tribulation is primarily the execution of God’s wrath on the earth. This wrath, as we will see from the following verses, is different from what we have now. It is much more intense and with a purpose. Here, without any comment, is a few references on the One who will bring wrath to the earth during the Tribulation period. Notice, for emphasis the bold type.
Behold, the Lord lays the earth waste, devastates it, distorts its surface, and scatters its inhabitants. 2 And the people will be like the priest, the servant like his master, the maid like her mistress, the buyer like the seller, the lender like the borrower, the creditor like the debtor. 3 The earth will be completely laid waste and completely despoiled, for the Lord has spoken this word. 4 The earth mourns and withers, the world fades and withers, the exalted of the people of the earth fade away. 5 The earth is also polluted by its inhabitants, for they transgressed laws, violated statutes, broke the everlasting covenant. 6 Therefore, a curse devours the earth, and those who live in it are held guilty. Therefore, the inhabitants of the earth are burned, and few men are left.
21 For behold, the Lord is about to come out from His place
To punish the inhabitants of the earth for their iniquity;
And the earth will reveal her bloodshed,
And will no longer cover her slain.
Alas for the day!
For the day of the Lord is near,
And it will come as destruction from the Almighty.
And I will bring distress on men,
So that they will walk like the blind,
Because they have sinned against the Lord;
And their blood will be poured out like dust,
And their flesh like dung.
18 Neither their silver nor their gold
Will be able to deliver them
On the day of the Lord’s wrath;
And all the earth will be devoured
In the fire of His jealousy,
For He will make a complete end,
Indeed a terrifying one,
Of all the inhabitants of the earth.
And the kings of the earth and the great men and the commanders and the rich and the strong and every slave and free man, hid themselves in the caves and among the rocks of the mountains; 16 and they said to the mountains and to the rocks, “Fall on us and hide us from the presence of Him who sits on the throne, and from the wrath of the Lamb; 17 for the great day of their wrath has come; and who is able to stand?”
“And the nations were enraged, and Thy wrath came, and the time came for the dead to be judged, and the time to give their reward to Thy bond-servants the prophets and to the saints and to those who fear Thy name, the small and the great, and to destroy those who destroy the earth.”
And I saw another angel flying in midheaven, having an eternal gospel to preach to those who live on the earth, and to every nation and tribe and tongue and people; 7 and he said with a loud voice, “Fear God, and give Him glory, because the hour of His judgment has come; and worship Him who made the heaven and the earth and sea and springs of waters.”
And another angel, a third one, followed them, saying with a loud voice, “If anyone worships the beast and his image, and receives a mark on his forehead or upon his hand, 10 he also will drink of the wine of the wrath of God, which is mixed in full strength in the cup of His anger; and he will be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb.
And another angel, the one who has power over fire, came out from the altar; and he called with a loud voice to him who had the sharp sickle, saying, “Put in your sharp sickle, and gather the clusters from the vine of the earth, because her grapes are ripe.” 19 And the angel swung his sickle to the earth, and gathered the clusters from the vine of the earth, and threw them into the great wine press of the wrath of God.
And one of the four living creatures gave to the seven angels seven golden bowls full of the wrath of God, who lives forever and ever.
And I heard a loud voice from the temple, saying to the seven angels, “Go and pour out the seven bowls of the wrath of God into the earth.”
And I heard the altar saying, “Yes, O Lord God, the Almighty, true and righteous are Thy judgments.”
And the great city was split into three parts, and the cities of the nations fell. And Babylon the great was remembered before God, to give her the cup of the wine of His fierce wrath.
After these things I heard, as it were, a loud voice of a great multitude in heaven, saying,
“Hallelujah! Salvation and glory and power belong to our God; 2 because His judgments are true and righteous; for He has judged the great harlot who was corrupting the earth with her immorality, and He has avenged the blood of His bond-servants on her.”