After the third angel turns the rivers and springs to blood by pouring the passion of God into them, the “angel of the waters” praises the righteous judgment of God (Revelation 16:5-7). His speech of praise is chiastically arranged, with a modification:
A. I heard the angel of waters saying
B. Just are you . . . . because You did judge
C. They poured out the blood of saints and prophets
C’. You gave them blood to drink. They are worthy.
A’. And I heard the altar saying
B’. Yes, Lord, for truth and just are Your judgments.
The chiasm structurally reinforces the message of eye-for-eye, blood for blood justice. The structure is a mirror image, describing the mirroring judgment of God. The interruption of the strict chiasm highlights another mirroring structure, actually an echo: What the angel of the waters says is repeated by the altar. The two lines amount to a two-strophe verse of a Psalm.
Beyond the chiasm, we have an intricate numerological patterning. In Greek, both B and B’ are twelve words in length (B: dikaios ei o on kai o en o osios oti tauta ekrinas; B’: nai kurie o theos o pantokrator alethinai kai dikaiai ai kriseis sou). Together, C and C’ consist of 13 words: oti aima agion kai propheton exechean kai aima autois dedokas piein axioi eisin). If we exclude the conjunction oti, the central statement again has twelve words. Alternatively, we can read verse 6 as two clauses, divided by kai, and each clause consists of six words.
The two “I heard” statements frame and interrupt the chiastic structure. John first hears the angel of waters speak, and his introduction consists of seven words (kai ekousa tou aggelou ton udaton legontos). John announces the speech of the altar with a briefer, five-word clause: kai ekousa tou thusiasteriou legontos. Together, these two announcements have twelve words.
Thus, the numerological pattern is:
A. A seven-word introduction of the angel.
B. A twelve-word praise.
C. Two six-word clauses, divided by “and.”
A’. A five-word introduction of a new speaker, the altar.
B’. A twelve-word praise.
What does it all mean? Why are these statements organized by twelves rather then by multiples of 3 or 7? I don’t know. I only observe and report.