A.T. Robertson Commentary Revelation 12:4

"And his tail draweth the third part of the stars of heaven, and did cast them to the earth: and the dragon standeth before the woman that is about to be delivered, that when she is delivered he may devour her child." — Revelation 12:4 (ASV)

His tail (η ουρα αυτου). See 9:10,19.

Draweth (συρε). Present active indicative of συρω, old verb, to drag, here alone in the Apocalypse, but see Joh 21:8.

The third part of the stars (το τριτον των αστερων). Like a great comet is this monster. See Da 8:10. Perhaps only the third is meant to soften the picture as in Re 8:7f.

Did cast them (εβαλεν αυτους). Second aorist active indicative. Charles takes this to refer to a war in heaven between the good angels and Satan, with the fall of some angels (Jude 1:6). But John may have in mind the martyrs before Christ (Hebrews 11:32f.) and after Christ's ascension (Matthew 23:35).

Stood (εστηκεν). Imperfect active of a late verb, στηκω, from the perfect εστηκα of ιστημ, graphic picture of the dragon's challenge of the woman who is about to give birth.

When she was delivered (οταν τεκη). Indefinite temporal clause with οταν and the second aorist active subjunctive of τικτω, "whenever she gives birth."

That he might devour (ινα καταφαγη). Purpose clause with ινα and the second aorist active subjunctive of κατεσθιω, to eat up (down). Cf.Jeremiah 28:34. This is what Pharaoh did to Israel (Exodus 1:15–22; Psalms 85:13; Isaiah 27:1; Isaiah 51:9; Ezekiel 29:3). Precisely so the devil tried to destroy the child Jesus on his birth.