'Pouring out the vials upon the earth, which contained the plagues,' in Revelation 16:1, signifies influx of the reformed into the church, or into people who study and receive the doctrine of justification by faith alone.

(Odkazy: Apocalypse Explained 16; Apocalypse Revealed 676)

10. Verse 2. Who bare witness to the Word of God, and to the testimony of Jesus Christ, signifies to those who in heart acknowledge Divine truth, and the Divine of the Lord in His Human. This is evident from the signification of "bearing witness," as meaning to acknowledge in heart (of which hereafter), and from the signification of "the Word," or speech of God, as meaning Divine truth (SeeArcana Coelestia 4692, 5075, 9987); and from the signification of "[the testimony of] Jesus Christ," as meaning the acknowledgment of the Lord's Divine in His Human. This is signified by "the testimony of Jesus Christ," because "to testify" signifies to acknowledge in heart, and to acknowledge Jesus Christ in heart is to acknowledge the Divine in His Human; for he that acknowledges the Lord, and does not at the same time acknowledge the Divine in His Human, does not acknowledge the Lord; since His Divine is in His Human, and not out of it; for the Divine is in Its Human as the soul is in the body, consequently to think of the Lord's Human, and not at the same time of His Divine, is like thinking of a man abstractly from his soul or life, which is not thinking of a man.

[2] That the Lord's Divine is in His Human, and that together they are one person, the doctrine received throughout the Christian world teaches; which teaching is as follows: "Although Christ is God and Man, yet they are not two, but one Christ; one, but not by a change of the Divine into the Human, but the Divine took the Human to Itself. Altogether one, not by confusion of the two natures, but by unity of person; for as soul and body make one man, so God and Man are one Christ" (Athanasian Creed). From this it is manifest, moreover, that those who separate the Divine into three persons, when they think of the Lord as a second person, ought to think of both together, the Human and the Divine; for it is said that they are a single person, and that they are one, as soul and body are. Therefore those that think otherwise do not think of the Lord; and those that do not think of the Lord in that way are unable to think of the Divine that is called the Father's, for the Lord saith:

I am the way, the truth, and the life; no one cometh unto the Father but through Me (John 14:6).

Since this acknowledgment is signified by the "testimony of Jesus Christ," it is said that:

The testimony of Jesus is the spirit of prophecy (Revelation 19:10).

"The spirit of prophecy" is the life and soul of doctrine (that "spirit" in the internal sense of the Word, signifies life or soul, may be seen Arcana Coelestia 5222, 9281, 9818; and that "prophecy" signifies doctrine, n. 2534, 7269); and the acknowledgment of the Lord is the very life or soul of all doctrine in the church. But of this more will be said in what follows.

[3] To "bear witness" is to acknowledge in heart, because spiritual things are treated of; and no one can bear witness respecting spiritual things except from the heart, because from no other source does he perceive that they are so. To bear witness of things that have existence in the world is to bear witness from knowledge, or from memory and thought, because the man has so seen or heard; but it is otherwise with things spiritual, for these fill the whole life and constitute it. The spirit of man, in which his life primarily resides, is nothing else than his will or his love, and his understanding and faith therefrom, and "heart" in the Word signifies the will and love, and understanding and faith therefrom. From this it is evident whence it is that by "bearing witness" in the spiritual sense, is meant to acknowledge in heart. Since by the "heart" is signified the good of love, and this alone is what acknowledges Divine truth, and the Divine of the Lord in His Human, and since that good is signified by "John," it is also said by John that he "bears witness to the Word of God and to the testimony of Jesus Christ." So also in another place:

And he that hath seen hath borne witness, and his witness is true; and he knoweth that he saith true, that ye may believe (John 19:35);

and in another place:

This is the disciple that beareth witness of these things, and wrote these things; and we know that his witness is true (John 21:24).