Poole on Revelation 7:3: The Seal of the Living God
Verse 3: Saying, (Rev. 6:6; 9:4) Hurt not the earth, neither the sea, nor the trees, till we have (Ezek. 9:4; Rev. 14:1) sealed the servants of our God (Rev. 22:4) in their foreheads.
[Do not (He speaks with authority, even indeed peremptory authority [Durham]) harm the earth, etc.] That is, Do not introduce diseases and plague by holding the winds (Ribera, Menochius). Inflict neither desolation upon the earth, nor massacre upon the peoples, nor conflagration upon the cities or Temple (Grotius). Do not harm the men living in any of those places (Camerarius).
[Till we seal (namely, with that signet of God, of which mention was just now made [Piscator]: we seal, that is, we cause to be sealed, namely, the Teachers of the Gospel by moving them to teach, and men by exhorting them inwardly to faith [Ribera]) the servants of our God (whom we worship, namely, I and those that are with me to help me in this sealing [Piscator on verse 1]: He here calls those that adhere to God in the time of apostasy the servants of God: Now, Christ says our God, as in John 20:17, my God and your God, for He is the Mediator and Head of His body [Durham]: Note the progression: Christ, in Revelation 3:12, calls God His own; now He makes God common to Himself and to us [Cotterius]) on their foreheads] As in Revelation 14:1 (Cluverus). With a obvious mark (Cotterius, Napier), so that it might be public (Cluverus), and might appear at first sight, as it were, who are true and Orthodox Christians (Gravius). We seal those things that we wish to keep safe. Now, on the forehead, because it was the custom in the East to write the names of masters upon the foreheads of servants, as it appears both from Ezekiel 9, and from Aristophanes, who introduced into a scene Babylonian servants with foreheads inscribed. And it was a custom among Christians to rub the forehead with the seal of the cross, as Tertullian, in Of the Crown, and Julian, in Cyril’s work, and other testify (Grotius). Others: On the forehead after the fashion of men, who, if they wish anything to be able to be easily distinguished from common things, impress a conspicuous mark upon it. Not that this seal would be perceptible to Antichrist or His ministers; for the world was not seeing those sealed, neither was it able to become acquainted with their song, Revelation 14:3, but, by this form of speech, the certain protection of them by the providence of their God is denoted (Forbes). There is an allusion, either, 1. to the ancient rite by which servants and soldiers were wont to be marked with the brand and inscribed with the name of him to whom they had pledged their faith (Mede’s Works 525, 699). Or, 2. to the custom of shepherds, who mark their own sheep (Napier). Or, 3. to the custom of Kings, who seal with their own Seal what they do not want to be touched (Durham’s Commentary upon the Book of Revelation 380). Or, 4. to the typical sealings (Cluverus, similarly Pererius) by which were formerly distinguished (Cluverus), the High Priests of the Jews [from others] by the golden plate on the forehead, etc. (Pererius), the Israelites from the Egyptians, Exodus 12:13 (Cluverus, Pererius, Durham), Rahab from those being destroyed, Joshua 2:18 (Cluverus), those lamenting from the rest, Ezekiel 9:4 (Cluverus, Pererius, Durham, Forbes). There the Angel is commanded to seal with a ת, which signifies the Law [תּוֹרָה/Torah], those that had kept the Law; even so that they might be unharmed in that time during which the Chaldeans were going to break in upon Jerusalem. So also here the Christians that were in Jerusalem and in all Judea were commanded to be sealed with the Cross, the mark of Christians, so that they might be exempted from the common evil of the Jews (Grotius). For this enigmatic sealing on the forehead clearly agrees unto that time in which Eusebius, in his Ecclesiastical History 3:5 [see the words in Grotius], says that Christians escaped, and departed unto Pella; not only before the siege, but also before the Jewish war against the Romans (Grotius, similarly Hammond). Now, in the siege not one Christian was left in the city. See Josephus’ Jewish War 2:22 (Hammond). Others: When the seventh Seal, which is of the Trumpets, was about to be opened, and the gales of calamities were about to be loosed at the sounding of the Trumpets, were going sweep across the earth (Mede’s Works 529), and were going to bring ruin upon the Roman state (Mede’s Works 563), it is foreseen by the Elect servants of God with the seal (Mede’s Works 529); and those with the impressed mark are distinguished, lest they should be destroyed with the rest. And certainly the event that obtained is after the likeness of a miracle, inasmuch as, although the Roman Empire was dissipated and destroyed with such a great overthrow of cities and men, the Church would endure in that very place in the midst of these evils; indeed, with the Beast defiling all Christianity at that time with idolatrous worship, notwithstanding he would cherish in his own bosom this elect Assembly intact. It was to be preserved by the seal of so great a God (Mede’s Works 563). In this place is shown the singular providence of Christ in stirring up pious Teachers, that would oppose heretics, and confirm the faithful even under the corrupt state of the Church. Now, the sealing here is properly understood, not as the internal sealing of the Holy Spirit in hearts, although this is implied, or rather presupposed, in the case of the elect; but as the external sealing, which is accomplished through the external confession of Orthodox truth (Gravius). This seal is able to be, either, 1. sensible (Ribera), namely, the sign of the Cross, with which the baptized are fortified (Ribera, Menochius). Which is foolish, for many, not at all elect, are sealed with this sign (Cluverus). Or, 2. invisible, so that the Angels in their own minds distinguish those that in the midst of the threats and bloodshed of Antichrist will not be ashamed to confess the Cross and Christ, and will dare openly to discountenance the crimes of the impious (Ribera). The seal here is understood of corporal preservation, but not of sanctification. For the seal of sanctification, 1. is not committed to Angels, but to the Spirit of God, Ephesians 4:30: 2. is in the heart: 3. is common to all believers: 4. exempts not from corporal danger, Revelation 11:7; 13:7: 5. and is given successively throughout all ages, and diversely to diverse persons, some more, others less. Now, this seal, 1. is committed to the Angels, verses 2 and 3: 2. is on the forehead: 3. is peculiar to those concerning whom it is here spoken: 4. preserves bodies, Revelation 9:4: 5. is given once and at the same time and to all equally (Anonymous).
Till we have sealed: A manifest allusion to Ezekiel 9:4, and, as some think, to the usage of some eastern countries, for masters to set their names upon the forehead of their slaves, by which they were known to be theirs, as we mark our sheep or other beasts. Men as vainly dispute what this seal should be, as what the תmeant in Ezekiel 9, the mark set upon those that mourned for the abominations of Jerusalem. The place where they were to be sealed signified the end of their sealing to be not so much for confirmation, for which seals are used, as notification, to signify to others they belong to God; so as it was of the same use as the blood upon the two side-posts and the upper doorposts of the Israelites in Egypt, Exodus 12:13.
 Greek: λέγων, Μὴ ἀδικήσητε τὴν γῆν, μήτε τὴν θάλασσαν, μήτε τὰ δένδρα, ἄχρις οὗ σφραγίσωμεν τοὺς δούλους τοῦ Θεοῦ ἡμῶν ἐπὶ τῶν μετώπων αὐτῶν. De Corona.  Cyril of Alexandria wrote Against Julian the Apostate.  Ezekiel 9:4b: “…Go through the midst of the city, through the midst of Jerusalem, and set a mark (תָּו) upon the foreheads of the men that sigh and that cry for all the abominations that be done in the midst thereof.”  Pella was a village on the eastern side of the Jordan, about half way between the River Jabbok and the Sea of Galilee.