Revelation 15:1: And I saw another sign in heaven, great and marvellous.

In Revelation 11:15, the seventh angel of the seventh seal blew his trumpet to introduce the Third Woe, but few details were given in the final verses of chapter 11.¹ John's chronological narrative was quickly interrupted by the three flashback chapters from Revelation 12 to 14. John's chronological account of the Third Woe now resumes in Revelation chapter 15 to add the missing details that were not given in Revelation chapter 11.²

John's expanded vision of the Third Woe begins with another sign in heaven.³ Unlike the symbolic signs that John saw in heaven from the premortal existence in Revelation chapter 12,⁴ the great and marvellous sign in Revelation 15:1⁵ will literally appear to the view of mortal people throughout the earth.⁶ It is the final heavenly sign before Christ's Second Coming.⁷ Joseph Smith called it the grand sign of the Son of Man.⁸

The Lord has not revealed specific details about what this Grand Sign will look like.⁹ However, Joseph Smith said it will be "as the light of the morning cometh out of the east."¹⁰ This implies that the Grand Sign will become increasingly bright or obvious until the Savior appears as a flaming fire brighter than any noon-day sun.¹¹ Some scholars have suggested that the Grand Sign may be the city of Enoch as it returns in great glory to earth from heaven.¹² If true, the Grand Sign would also include the glory of all exaltation-worthy saints as they rise up to stand with Christ on heavenly mount Zion when the morning of the first resurrection resumes at the end of the Second Woe and immediately before the start of the Third Woe.¹³ Whatever its form may be, the elect who stand with Christ on heavenly mount Zion will undoubtedly recognize the Grand Sign for what it is and they may even be part of it.¹⁴ Spiritually unenlightened observers on earth,¹⁵ on the other hand, will say it is a planet, a comet, etc.¹⁶ They will ignore the Grand Sign as they ignore the many other latter-day signs and omens that precede it.¹⁷

Jesus prophesied in Matthew 24:30 that after the Grand Sign appears, "then shall all the tribes of the earth mourn."¹⁸ This will undoubtedly be the case when the final seven Vial Plagues are poured out on the earth. This may also refer to the mourning of Jewish people who survive the final Abomination of Desolation¹⁹ and live to see the Savior appear on the mount of Olives.²⁰ These Jewish survivors will mourn when they recognize Christ as the Messiah whom they crucified.²¹ The remaining earthly tribes (telestial people)²² in all the world will mourn²³ as God's destructive judgments fall upon them during the Third Woe.²⁴