A.T. Robertson Commentary Revelation 15:5

"And after these things I saw, and the temple of the tabernacle of the testimony in heaven was opened:" — Revelation 15:5 (ASV)

The temple of the tabernacle of the testimony (ο ναος της σκηνης του μαρτυριου). Charles calls this "strange" language. Probably the tabernacle or tent of witness (Numbers 9:15; Numbers 17:7) is in mind and the tent of meeting (Exodus 27:21 rather than the temple in Jerusalem.

Was opened (ηνοιγη). Second aorist passive indicative of ανοιγω as in 11:19. For ναος see 3:12; 7:15; 14:15,17; 16:1,17.