And I saw another angel ascending from the rising of the sun, having the seal of the living God. He cried out with a loud voice to the four angels, to whom it was given to harm the earth and the sea, saying, “Do not harm the earth, the sea or the trees, until we have sealed the servants of our God upon their foreheads.” Rev 7:2-3.
The setting of Revelation 7 is the last verse of chapter 6. "For the great day of his wrath has come, and who is able to stand?" (Rev 6:17). The purpose of Revelation 7 is to provide the answer to this question at the end of Revelation 6: "Who (at the time of the end) is able to stand?" The answer comes in two parts: The 144,000 (7:1-8) and a great multitude (7:9-17).
There is a chilling background to this passage. The scene is Jerusalem, the year is probably 586 BC. In vision, Ezekiel's companion calls for the guards of the city to come. Ezekiel watches as six terrifying men approach the temple from the north with deadly weapons in their hands. A seventh man is with them and he has a writing kit at his side. The seven men enter the temple courts and stand by the altar of burnt offering.
9Then a stunning thing happens. The shekinah glory of God rises up from the ark and moves out to the door of the temple, visible to all! God Himself calls out to the man with the writing kit and says, "Go throughout the city of Jerusalem and put a mark on the foreheads of those who grieve and lament over all the detestable things that are done in it." Then He orders the other six to follow him and slaughter old and young, male and female, without showing pity or compassion. "But do not touch anyone who has the mark. Begin at my sanctuary." And the men begin the slaughter among the elders standing in front of the temple (Ezek 9:1-7).
This scene is one of the most frightening, most sobering texts in all the Bible. It is a symbolic description of events that took place almost literally in the destruction of Jerusalem in Ezekiel's day. God drew a distinction between those who were on His side (sighing and crying for the abominations of the people) and those who would be slain.
Revelation 7 seems to offer a glimpse of the final events of earth's history: a final proclamation, marks on the forehead, the world called into judgment, and God rescuing His people. In the end God's discerning eye can tell who is committed to Him and who is not. God's people have often suffered at the hands of others in the name of God. At the end God will make clear to all exactly who belongs to Him.