The dragon, the beast, and the false prophet collaborate to send unclean messages into the world. That there are three
identical spirits demonstrates the unity of their message and their purpose.
The term unclean
appears frequently in Old Testament ceremonial law to describe what is opposite to a God who is of purer eyes than to behold evil (Habakkuk 1:13). Anything that hinted at sin (and/or its effects) was unclean
for Israel. That something unclean
comes from the mouths of these three creatures indicates that their words (and hearts) are contrary to God.
What come from their mouths are spirits like frogs.
Frogs were among the unclean creatures for Israel (Leviticus 11:10, Leviticus 11:42). From the reference to the mouth
of the three creatures it is evident that the point of the comparison with frogs is not the appearance of this amphibian or the nature of its habitat but is instead the sound it makes. The nonsense coming from the mouths of the dragon, the beast, and the false prophet is no more sensible than the croaking of a frog. This contrasts with the purity and clarity of the words that come from God.
13 And I saw, coming out of the mouth of the dragon and out of the mouth of the beast and out of the mouth of the false prophet, three unclean spirits like frogs.