We believe the Bible describes two classes of redeemed; namely, the great multitude, which began with Adam and goes through the close of probation, and a group of 144,000 in number.

The sealing work of the 144,000 began with the proclamation of the third angel’s message. Through their obedience to the Ten Commandments, they demonstrate their faithfulness. They distinguish themselves by their observance of the Sabbath, which represents the seal of God. We believe the sealing work will continue until the close of probation. Spiritual Israel will be gathered from all nations, kindreds, and tongues. 
Revelation 7:2-8 – 
And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea, Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads. 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. Of the tribe of Juda were sealed twelve thousand. Of the tribe of Reuben were sealed twelve thousand. Of the tribe of Gad were sealed twelve thousand. Of the tribe of Aser were sealed twelve thousand. Of the tribe of Nephthalim were sealed twelve thousand. Of the tribe of Manasses were sealed twelve thousand. Of the tribe of Simeon were sealed twelve thousand. Of the tribe of Levi were sealed twelve thousand. Of the tribe of Issachar were sealed twelve thousand. Of the tribe of Zabulon were sealed twelve thousand. Of the tribe of Joseph were sealed twelve thousand. Of the tribe of Benjamin were sealed twelve thousand. 
Revelation 14:1-5 – 
And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree. And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea, Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads. 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. Of the tribe of Juda were sealed twelve thousand. Of the tribe of Reuben were sealed twelve thousand. Of the tribe of Gad were sealed twelve thousand.

The seal of God is a sign of redemption. All who choose Jesus Christ as their Saviour and place themselves under His guidance will experience a change in their characters. They receive His righteousness; and under the influence of the Holy Spirit, they become more and more like Christ and bring forth fruits of obedience. One of these fruits is the observance of the holy Sabbath, which is referred to as the seal or sign of the affiliation between God and the believers.
Ezekiel 20:12, 20 – 
Moreover also I gave them my sabbaths, to be a sign between me and them, that they might know that I am the LORD that sanctify them… And hallow my sabbaths; and they shall be a sign between me and you, that ye may know that I am the LORD your God.

The sleeping sealed ones, through a special resurrection shortly before the return of Christ, will be united with the living sealed believers. Together they will hear the voice of God proclaim the covenant of peace with His people. As “first fruits” of redemption, they will witness Christ’s second coming, see the great multitude resurrected, and ascend with it to be received by Christ. 
Daniel 12:1, 2 – 
And at that time shall Michael stand up, the great prince which standeth for the children of thy people: and there shall be a time of trouble, such as never was since there was a nation even to that same time: and at that time thy people shall be delivered, every one that shall be found written in the book. And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. 
Revelation 1:7 – 
Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.

“The sign, or seal, of God is revealed in the observance of the seventh-day Sabbath, the Lord’s memorial of creation.”

“The mark of the beast is the opposite of this – the observance of the first day of the week.” – Testimonies for the Church, vol. 8, p. 117.

“The fourth commandment alone of all the ten contains the seal of the great Lawgiver, the Creator of the heavens and the earth.” – Testimonies for the Church, vol. 6, p. 350.