Then they heard: to avoid any ambiguity it is better to make the subject explicit, “Then the two prophets heard.” Some manuscripts have “I heard,” a text preferred by some commentators and New Jerusalem Bible (also NRSV margin); Revised English Bible uses the passive, “A loud voice was heard.” It seems best to have the two prophets as the subject.

A loud voice from heaven: see 10.4, 8. This is either God or an angel speaking. Alternative translation models for this first sentence are: “Then the two prophets heard someone speaking to them in a loud voice from heaven” or “Then a loud voice from heaven said to the prophets.”

In the sight of their foes: this is more naturally expressed by “as their enemies watched” (Good News Translation), “while their enemies were watching them,” or “while the people who hate them….” For their foes see 11.5 (“foes”).

They went up to heaven in a cloud: the Greek preposition translated to by Revised Standard Version may mean “into” (Good News Translation); either meaning fits the context. A cloud serves as their transportation to heaven (see Acts 1.9; similar is the whirlwind of 2 Kgs 2.11).

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 .