Reward her even as she rewarded you, and double unto her double according to her works: in the cup which she hath filled fill to her double.
I want to take a moment to explain some of the verses in the Bible that refer to paying back double when someone is wronged. The doubling back of payment such as found in Revelation 18:6 is not just a random number that that John came up with when he was penning the revelation of the Messiah. The actual number of paying back double comes from the Law of Moses on restitution which is found in Exodus 22. Specific examples in Exodus 22 are located in verses 4,7, and 9. I am sure there are other examples in the Bible that would expound on the concept of this law. If you read Exodus 22, then you will realize that the examples given of paying back double is for the times when whatever was taken can be recovered and returned to its rightful owner. In the particular case of Revelation 18:6 when the Messiah comes he takes possession of the kingdom and the payback is double which means the world is not destroyed by nuclear weapons or some other way, otherwise the payback would be five times.
An actual example of how this law works
This is an actual example that happened to me. I borrowed a wrench from a man that I work with and because of where I was working, I lost the wrench. I told the man that I would buy him two wrenches in return. He told me that one would be enough and not to bother with two. I then explained to him that it is a religious obligation for me and I had to buy two wrenches for him and he agreed to let me do it. Later on, I found the wrench and was able to return it to him.
Although this law may be different than the way most Americans think, it does work. With the example given above, if I had not returned the wrench then the man would be without his property. Taking another's property, not returning it, and not making restitution for the property no matter what you call it, it is theft. Under the current edicts of mans law if someone steals something and the thief is prosecuted and put in jail, then the proper owner of the property will he not only get his property back, but is also taxed to house a criminal, essentially making him a victim twice. Under Yahweh's law of restitution, you are at the very least, assured to be repaid double if someone doesn't return your property. If you don't get repaid, then the person is breaking the 8th Commandment by stealing and if they refuse to follow the laws of Yah then then it's called heresy and is a capital offense.
What is great about this law
Under Yah's laws you are more likely to let others borrow what you own by sharing. I would be willing to loan anything to anyone in need if I were to be guaranteed that I would receive double of whatever I loan out and it doesn't get returned, or five times if the property is purposely destroyed. This law also makes the person doing the borrowing think twice about whether or not if they absolutely need to borrow the object to begin with. It also guarantees that they would be careful with your property and return it promptly and as the owner you wouldn't have to go looking for it.
The laws of Yahweh are perfect and will be the law of the land when his kingdom is restored on earth. Israel will rule by the very laws of Yahweh. It will be a glorious day when the kingdom is restored on earth and when everyone on the planet will be treated fairly. Although this is only one example of what will change, we must look forward to the future by not sinning, Sinning of course means we must be willing to follow his laws 1 John 3:4.