John had mentioned in Revelation 17:4 that the prostitute held in her hand “a golden cup full of abominations and the impurities of her sexual immorality.” Presumably as a result of drinking the content of this cup, she was “drunk with the blood of the saints” (Revelation 17:6). This, then, was “the cup she [had] mixed.” Now the heavenly voice commands his people (mix
is a plural imperative) to prepare an exact equivalent that Babylon must drink, but this time she will not drink it with pleasure but as a punishment for her iniquities.
It should be noted that the term “cup” occurs repeatedly in the Old Testament in the context of God's pouring out his wrath (e.g., Psalm 75:8). The unspoken implication is that she will drink it this time with revulsion.
6 Pay her back as she herself has paid back others, and repay her double for her deeds; mix a double portion for her in the cup she mixed.