Elder Bruce R. McConkie:

“To have one’s calling and election made sure is to be sealed up unto eternal life; it is to have the unconditional guarantee of exaltation in the highest heaven of the celestial world; it is to receive the assurance of godhood; it is, in effect, to have the day of judgment advanced, so that an inheritance of all the glory and honor of the Father’s kingdom is assured prior to the day when the faithful actually enter into the divine presence to sit with Christ in his throne, even as he is ‘set down’ with his ‘Father in his throne.’ (Rev. 3:21.) (Doctrinal New Testament Commentary, Bookcraft, 1973, 3:330–31.)

Doctrine and Covenants 131:5 - 6

5  (May 17th, 1843.)  The more sure word of prophecy means a man's knowing that he is sealed up unto eternal life, by revelation and the spirit of prophecy, through the power of the Holy Priesthood.

6  It is impossible for a man to be saved in ignorance. 

2 Peter 1:10 – 11

10  Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall:

11  For so an entrance shall be ministered unto you abundantly into the everlasting kingdom of our Lord and Saviour Jesus Christ. 

Elder Bruce R. McConkie:

As Elder McConkie goes on to indicate, the “unconditional guarantee” means that a person’s actions have been fully approved, that “there are no more conditions to be met by the obedient person.” (P. 335.) When one has been thus sealed up unto eternal life, he is “sealed up against all manner of sin except blasphemy against the Holy Ghost and the shedding of innocent blood.” (Doctrines of Salvation, 2:46.)

The Prophet Joseph Smith’s exhortation to press forward to this goal of assured exaltation is as follows:

“I would exhort you to go on and continue to call upon God until you make your calling and election sure for yourselves, by obtaining this more sure word of prophecy, and wait patiently for the promise until you obtain it.” (Teachings, p. 299.)