A.T. Robertson Commentary Revelation 13:6

"And he opened his mouth for blasphemies against God, to blaspheme his name, and his tabernacle, [even] them that dwell in the heaven." — Revelation 13:6 (ASV)

For blasphemies (εις βλασφημιας). "For the purpose of blasphemies."

Against God (προς τον θεον). "Face to face with God" in sheer defiance, like Milton's picture of Satan in Paradise Lost. See Da 7:25; 8:10. The aorist ηνοιξεν is probably constative, for he repeated the blasphemies, though the phrase (ανοιγω to stoma, to open the mouth) is normally ingressive of the beginning of an utterance (Matthew 5:2; Acts 8:35). This verse explains verse 5. The Roman emperors blasphemously assumed divine names in public documents. They directed their blasphemy against heaven itself ("his tabernacle," την σκηνην αυτου, 7:15; 12:12; 21:3) and against "them that dwell in the heaven" (τους εν τω ουρανω σκηνουντας), the same phrase of 12:12 (either angels or the redeemed or both).