The 144,000 Servants in Revelation 7:4-8 will be sealed primarily during the sixth seal. However, this work in the sixth seal will be the end of a preparatory process rather than the beginning.¹ The process of sealing the 144,000 Servants began after the death and resurrection of Jesus Christ² in approximately 34 AD.³ This corresponds with the period of the fifth seal,⁴ when vicarious work for the dead began for the first time.⁵ Baptism for the dead was a recognized doctrine and practice during the apostolic period.⁶ However, very few baptisms and other temple ordinances were performed, either for the living or for the dead, due to the onset of the Great Apostasy.⁷ This limiting factor has made temple work the most important and urgent work to be accomplished during the period of the sixth seal.⁸

In addition to the limited sealings that occurred during the fifth seal, Joseph Smith confirmed that sealings of the 144,000 Servants were also underway during his life.⁹ Doctrine and Covenants Section 77:10-11 states that sealings of the 144,000 will be accomplished¹⁰ before the physical calamities at the end of the sixth seal.¹¹ Many sealings will be accomplished, but this does not mean that all such sealings will be complete by the end of the sixth seal. Sealings of the 144,000 Servants will continue during the seventh seal until the Second Coming for both the living and the dead.¹² Sealings must continue until that time so that living persons can also receive their earthly ordinances¹³ and come forth in the morning of the first resurrection¹⁴ to stand with Christ on mount Zion at the Second Coming.¹⁵ Some saints that are alive at the Second Coming will be quickened to stand with Christ on mount Zion but will return to live their remaining lives on earth as millennial mortals.¹⁶ This will undoubtedly include those living persons‒such as children and youth‒that have not received all their necessary temple ordinances as of the Second Coming.

During John's vision of the sixth seal he merely heard, but did not see, that the 144,000 Servants had been sealed.¹⁷ This symbolic distinction¹⁸ confirms that he heard that sealings of the 144,000 Servants were accomplished–but not all completed–before he then saw the destructive end of the sixth seal.¹⁹