Revelation 9:4

And it was commanded them, not to hurt the grass of the earth, neither any green thing, neither any tree, but only the men who have not the seal of God on their foreheads.

2 Corinthians 1:22

Who hath also sealed us, and given us the earnest of the Spirit in our hearts.

Revelation 14:1

And I saw and behold a Lamb standing on mount Sion, and with him an hundred forty-four thousand, having his name and the name of his Father written on their foreheads.

Revelation 7:2-3

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,

2 Timothy 2:19

But the foundation of God standeth fast, having this seal, The Lord knoweth those that are his: and, Let every one who nameth the name of the Lord depart from iniquity.

Revelation 20:4

And I saw thrones, and they sat on them, and judgment was given to them; and I saw the souls of them who had been beheaded for the testimony of Jesus, and for the word of God, and those who had not worshiped the wild beast nor his image, neither had received the mark on their forehead or on their hand; and they lived and reigned with Christ a thousand years.

2 Corinthians 12:21

and I should mourn over many of them who had sinned before, and have not repented of the uncleanness, and fornication, and lasciviousness, which they have committed.

Ephesians 4:30

And grieve not the Holy Spirit of God, whereby ye are sealed unto the day of redemption.

2 Peter 2:8-9

(For that righteous man dwelling among them, in seeing and hearing vexed his righteous soul from day to day with their unlawful deeds).

Revelation 13:6-7

And he opened his mouth in blasphemy against God, to blaspheme his name and his tabernacle, even them that dwell in heaven.

Treasury of Scripture Knowledge

Summary

And the LORD said unto him, Go through the midst of the city, through the midst of Jerusalem, and set a mark upon the foreheads of the men that sigh and that cry for all the abominations that be done in the midst thereof.

General references

Bible References

That sigh

2 Corinthians 12:21
and I should mourn over many of them who had sinned before, and have not repented of the uncleanness, and fornication, and lasciviousness, which they have committed.
2 Peter 2:8
(For that righteous man dwelling among them, in seeing and hearing vexed his righteous soul from day to day with their unlawful deeds).

General references

Matthew 5:4
Happy are they that mourn; for they shall be comforted.
Romans 9:2
That I have great sorrow and continual anguish in my heart.