6 Reward [apodidomi] her [autos] even [kai] as [hos] she [autos][houtos] rewarded [apodidomi] you, [humin] and [kai] double [diploo] unto her [autos] double [diplous] according to [kata] her [autos] works: [ergon] in [en] the cup [poterion] which [hos] she hath filled [kerannumi]
fill [kerannumi] to her [autos] double. [diplous] KJV-Interlinear
her back even as she has paid, and give back to her double according to her
deeds; in the cup which she has mixed, mix twice as much for her. NASB
The law of retaliation in justice is reserved for God, and never for man. An eye for an eye and tooth for a tooth, Matt 5:38; Ex 21:23-24; Lev 24:19-20; Deut 19:2, is in view here, but in the sense of double the crime, then double the punishment.
Double represents a fulfillment or completion of something. If something is done once, then double that thing is required to correct it. Such that anyone who presumes to pursue a crime will never gain anything, but lose as a result, ending up with much less than he started out.
God reserves the right of repayment, Jer 50:14-15; Ps 137:8; Jer 50:29; 51:24, 51:56; 'Vengeance is mine…' Rom 12:19-21.
The word for double, 'diplous,' literally means double the double things, and is here repeated in this verse, to emphasize the importance of no gain, only loss, results from evil. A wrong done against someone else is also a wrong performed by yourself, therefore double.
Double has been the evil of her infractions, and therefore double must be her punishment. The her, is of course the entire concept of Babylon, the harlot, the cosmos policy of Satan, the patterns of evil which humanity so easily pursues when truth is rejected.
Payment of double as punishment of crimes has been well documented in the Old Testament, Ex 22:4,7,9; Isa 40:1-2; Jer 16:18, 17:18, 51:7. This is not a guideline for repayment, but a concept that emphasizes the certainty of no gain in crime, as well as a thorough crushing of the evil doer.
The ultimate crime is of course unbelief, and the ultimate penalty is the Lake of Fire. Gaining all of the world today, will never compare to the eternal loss in the fires of hell.
The symbolism of the cup indicates that evil initiates, mixes, creates, invents all of its crimes, by itself. God does not invent or promote evil, and no one is guilty of evil except evil itself.
God will double the portion of the content of the cup in the same cup. That is to say, that God will use evil against itself, in effect punishing itself by means of its own practices, and doing doubly so.
Evil is the use of violence against innocents, and therefore the punishment of evil requires judgment of a greater violence against evil in order to eliminate it.
Therefore in so doing, evil being a violence is itself going to be destroyed by violence, eye for an eye, but double, tooth for a tooth, in order to eliminate it permanently.