Revelation 7 discusses this, and their purpose. 7:3 Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads. 4 And I heard the number of them which were sealed: and there were sealed an hundred and forty and four thousand of all the tribes of the children of Israel.
From what I can see, the Tribulation will not start until these 144,000 have been sealed.
Then in Rev 7: 9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;
10 And cried with a loud voice, saying, Salvation to our God which sitteth upon the throne, and unto the Lamb.
11 And all the angels stood round about the throne, and about the elders and the four beasts, and fell before the throne on their faces, and worshipped God,
12 Saying, Amen: Blessing, and glory, and wisdom, and thanksgiving, and honour, and power, and might, be unto our God for ever and ever. Amen.
13 And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
From what I read, these 144,000 saved a great amount of people during Great Tribulation. Especially from Rev 7:14
Also, In Revelation 14:3 - 9. And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred and forty and four thousand, which were redeemed from the earth.
4 These are they which were not defiled with women; for they are virgins. These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb.
5 And in their mouth was found no guile: for they are without fault before the throne of God.
6 And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people,
7 Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.
8 And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
9 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,
It has certainly been my opinion that that was the function of the 144000...as soon as they appear and witness, whole multitudes of folks appear to be saved out of the tribulation period.
It has certainly been my opinion that that was the function of the 144000...as soon as they appear and witness, whole multitudes of folks appear to be saved out of the tribulation period.
The reason the 144.000 are from the tribes of Israel is because during the Tribulation, God’s Holy Spirit will be evangelizing through the Jews since the Church Age has ended with the Rapture of The Church.