12. they--so A, C, and Vulgate. But B, Coptic, Syriac, and ANDREAS read, "I heard."
      a cloud--Greek, "the cloud"; which may be merely the generic expression for what we are familiar with, as we say "the clouds." But I prefer taking the article as definitely alluding to THE cloud which received Jesus at His ascension, Ac 1:9 (where there is no article, as there is no allusion to a previous cloud, such as there is here). As they resembled Him in their three and a half years' witnessing, their three and a half days lying in death (though not for exactly the same time, nor put in a tomb as He was), so also in their ascension is the translation and transfiguration of the sealed of Israel (Re 7:1-8), and the elect of all nations, caught up out of the reach of the Antichristian foe. In Re 14:14-16, He is represented as sitting on a white cloud.
      their enemies beheld them--and were thus openly convicted by God for their unbelief and persecution of His servants; unlike Elijah's ascension formerly, in the sight of friends only. The Church caught up to meet the Lord in the air, and transfigured in body, is justified by her Lord before the world, even as the man-child (Jesus) was "caught up unto God and His throne" from before the dragon standing ready to devour the woman's child as soon as born.

JFB.