Do not … until: God commands the four angels to hold back the winds for a short time. They must not harm the earth, the sea, or the trees until the servants of God receive his seal on their foreheads.
The seal of the living God signifies belonging to God's family; God owns and protects his people (2 Corinthians 1:22; Ephesians 1:13–14). In ancient times, sealing or tattooing showed ownership.
The angel carrying the seal identified God's people, answering who would survive God's wrath (Revelation 6:17; see Ezekiel 9:3–8; John 17:14–15) and furthering the promise of protection (Revelation 3:10; see also 11:1–2).