Albert Barnes 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)

And he opened his mouth in blasphemy against God, to blaspheme his name. By his own arrogant claims; by his assumed authority in matters of conscience; by setting aside the Divine authority; and by impious declarations in derogation of the Divine claims. See Barnes on Revelation 13:1.

And his tabernacle. Literally, "his tent"—skhnhn. This is the word that is commonly applied to the sacred tent or tabernacle among the Hebrews, in which the ark was kept, and which was the seat of Jewish worship before the building of the temple. It is thus used to denote a place of worship, considered as the dwelling-place of God, and is in this sense applied to heaven (Hebrews 8:2; Hebrews 9:11; Revelation 15:5).

It seems to be used here in a general sense to denote the place where God was worshipped; and the meaning is, that there would be a course of conduct in regard to the true church—the dwelling-place of God on the earth—which could properly be regarded as blasphemy. Let anyone remember the anathemas and excommunications uttered against the Waldenses and Albigenses, and those of kindred spirit that appeared in the long period of Papal rule, and he will find no difficulty in perceiving a complete fulfillment of all that is said here.

And them that dwell in heaven. The true worshippers; the members of the true church, represented as dwelling in this holy tabernacle. No one acquainted with the reproaches cast on the devoted and sincere followers of the Savior during the dark periods of Papal rule can fail to see that in those reproaches was a complete fulfillment of all that is predicted here.

that dwell (Hebrews 12:22–23)