In Exodus 9:23, 29, this signifies truths divine which enlighten and perfect people in heaven, but terrify people in hell. (Arcana Coelestia 7573)

In Psalm 29:3, this signifies the Word in its power. (Doctrine Regarding Sacred Scripture 18[4])

When the Lord speaks through the heaven, it descends into the lower spheres and is heard as thunder. As He speaks through the whole of heaven at once, the sound is called 'seven thunders' in Revelation 10. 'Seven' signifies all, everything, and wholeness. This is why 'thunder' signifies instruction and perception of truth, and in this instance, the revealing and manifestation of truth. A voice from heaven is heard as thunder when it comes from the Lord, which can be seen in John 12:28-30, Job 37:4-5, 2 Samuel 22:14, Revelation 14:2, and Psalms 81:8. 'Great thunder,' as in Revelation 14:2, signifies the divine good of divine love.

(Odkazy: Apocalypse Explained 10, 14 [2]; Apocalypse Revealed 472)

18. 3. The spiritual meaning is what causes the Word to be Divinely inspired and holy in every word. People in the church say that the Word is holy, and this because Jehovah God spoke it. But because its holiness is not apparent from the letter alone, therefore someone who once doubts its holiness on that account, later finds, when he reads the Word, many things in it to confirm himself in that doubt. For he asks himself then, “Is this holy? Is this Divine?”

Therefore, to keep this kind of thinking from flowing in and prevailing among many people, and so causing the conjunction of the Lord with the church where the Word is to perish, it has pleased the Lord now to reveal the spiritual sense, in order to make known in what the holiness in the Word lies.

[2] But let examples illustrate this as well:

The Word has as it subject sometimes Egypt, sometimes Assyria, sometimes Edom, Moab, the sons of Ammon, Tyre and Sidon, Gog. Someone who does not know that the names of these entities symbolize matters relating to heaven and the church may be led astray into the error of supposing that the Word has much to say about nations and peoples and only a little relating to heaven and the church, thus much about earthly matters and little about ones having to do with heaven. On the other hand, when he know what these entities or their names symbolize, it enables him to return from error into the truth.

[3] The same is the case when a person sees in the Word its frequent mention of gardens, groves, and forests, and the trees in them, such as olives, vines, cedars, poplars, and oaks, as well as the frequent mention of lambs, sheep, goats, calves, and oxen; and also of mountains, hills, and valleys, and the springs, rivers, and waters in them; and still more of the like. Someone who knows nothing of the Word’s spiritual meaning cannot help but believe that these are the only things meant. For he does not know that gardens, groves and forests mean wisdom, understanding and knowledge; that olives, vines, cedars, poplars and oaks mean the church’s celestial, spiritual, rational, natural and sensual goodness and truth; that lambs, sheep, goats, calves and oxen mean innocence, charity, and natural affection; that mountains, hills and valleys mean the higher, lower and lowest planes of the church; and that Egypt symbolizes knowledge, Assyria reason, Edom the natural component, Moab the adulteration of goodness, the sons of Ammon the adulteration of truth, Tyre and Sidon concepts of truth and goodness, and Gog outward worship without any internal worship.

However, when a person knows this, he is able then to see that the Word deals only with matters connected with heaven, and that the earthly expressions are simply the vessels in which these are contained.

[4] But let an example from the Word illustrate this too. We read in the book of Psalms:

The voice of Jehovah is upon the waters; the God of glory causes it to thunder; Jehovah is upon the great waters.... The voice of Jehovah breaks the cedars..., Jehovah shatters the cedars of Lebanon, and makes them skip like a calf, Lebanon and Sirion like the offspring of unicorns. The voice of Jehovah strikes like a flame of fire. The voice of Jehovah causes the wilderness to quake; (it) causes the wilderness of Kadesh to quake. The voice of Jehovah makes deer give birth, and strips the forests bare; but in His temple everyone says, “Glory!” (Psalms 29:3-9)

Someone who does not know that each and every word there is holy and Divine may say to himself, if he is a merely natural person, “What does it mean that Jehovah sits upon the waters, that He shatters cedars with His voice, that He makes them skip like a calf, and Lebanon like the offspring of unicorns, that He makes deer give birth?” And so on.

[5] That is because he does not know that in the spiritual sense these declarations describe the power of Divine truth or of the Word. For in that sense the voice of Jehovah, which in this case is thunder, means Divine truth or the Word in its power. The great waters on which Jehovah sits mean the falsities of the rational self. A calf and the offspring of unicorns mean the falsities of the natural and sensual self. A flame of fire means the affection accompanying falsity. A wilderness and the wilderness of Kadesh mean a church without any truth and one without any goodness. The deer which the voice of Jehovah causes to give birth mean gentiles possessing a natural goodness. And the forests which it strips bare mean the kinds of knowledge and concepts which the Word lays open to them. Consequently the passage says next, “in His temple everyone says, ‘Glory!’ ” which means that there are Divine truths in every constituent of the Word; for the temple symbolizes the Lord, and so also the Word, as well as heaven and the church, and glory symbolizes Divine truth.

It is apparent from this that there is no word in the passage that does not describe the Divine power of the Word against falsities of every kind in natural people, and the Divine power of reforming gentiles.