While one class receives the Mark of the Beast, another class receives the Seal of God:
And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.
Revelation 14:11
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,
Revelation 7:2,3
Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads.
Keeping God’s Commandments, including the Seventh Day Sabbath, is a sign that we are God’s people:
And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes.
Therefore shall ye lay up these my words in your heart and in your soul, and bind them for a sign upon your hand, that they may be as frontlets between your eyes.
Deuteronomy 6:8, 11:18
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.
Ezekiel 20:12