II Corinthians 1:21-22 NKJV
Now He who establishes us with you in Christ and has anointed us is God, 22 who also has sealed us and given us the Spirit in our hearts as a guarantee.
Ephesians 1:13-14 NKJV
In Him you also trusted, after you heard the word of truth, the gospel of your salvation; in whom also, having believed, you were sealed with the Holy Spirit of promise, 14 who is the guarantee of our inheritance until the redemption of the purchased possession, to the praise of His glory.
Ephesians 4:30 CSB
And don’t grieve God’s Holy Spirit. You were sealed by him for the day of redemption.
Revelation 9:4 GW ( The Fifth Trumpet [CSB] )
They were told not to harm any grass, green plant, or tree on the earth. They could harm only the people who do not have the seal of God on their foreheads.