God’s temple in heaven was opened: it is to be assumed that an angel opened the door of the heavenly temple. The phrase God’s temple is used also in 11.1, but there it refers to the Jerusalem Temple; here it is the heavenly temple (see 7.15). Some languages have special words for opened that can be both active and passive in this clause; for example, “God’s house (or, temple) in heaven opened up”; but in other languages one may have to say “Someone opened God’s temple in heaven.”

The ark of his covenant: in the Jerusalem Temple this was the wooden box that formerly contained the two stone tablets on which were inscribed the Ten Commandments. In the Jerusalem Temple the Covenant Box had been kept in the Most Holy Place (see 1 Kgs 8.1-9). The Hebrew and Greek words for covenant appear many times in the Bible, and a translation should have by now found the appropriate word or phrase to describe this relationship that God and Jesus Christ have established with the people of God. To avoid the passive, this clause may be expressed as “I saw the Covenant Box there.”

At the crucifixion of Jesus the heavy curtain that separated the Most Holy Place from the Holy Place was torn in two (Matt 27.51), and also at that time there was an earthquake.

Flashes of lightning, voices, peals of thunder, an earthquake, and heavy hail: see 4.5; 8.5, 7.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .