A belief that is unique to the LDS church is that of Eternal Families and Eternal Marriage. This restored practice is a cornerstone in the LDS faith and a key part to the Plan of Salvation. Though this practice of sealing families together for time and all eternity is not directly taught in the Bible, there are verses and teachings the give hints and clues that suggest it. By the power of the Holy Ghost and prayer, it can also be known that it is true.
"And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall bebound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven. Verily I say unto you, Whatsoever ye shall bind on earth shall be bound in heaven: and whatsoever ye shall loose on earth shall be loosed in heaven."
In verse 19, Jesus bestowed the priesthood to Peter, and will later bestowed it on the rest of the Twelve. Christ gives Peter the sealing keys of the priesthood, to bind or seal on earth and in heaven. This means that whatever Peter seals on earth by authority of the priesthood given to him, will also be sealed in Heaven. This includes baptism and marriages. The key is that Peter was given the proper authority to do so, by Christ. From there, Peter was able tobestow the keys and authority of the priesthood on to others who were called to the different priesthood offices.
"I know that, whatsoever God doeth, it shall be for ever: nothing can be put to it, nor any thing taken from it: and God doeth it, that men should fear before him."
This verse teaches that whatever God does is forever. We believe that marriage can be done by the power and authority of God, making it God’s work and thus lasting forever.
" Nevertheless neither is the man without the woman, neither the woman without the man, in the Lord."
Paul says in this verse that men and women are not separated in the Lord. Meaning that they will be together, in the presence of God. The doctrine of eternal marriage teaches that those who have been true to the covenants made at the time of their sealing, will live in the Celestial Kingdom, where God lives, as husband and wife for time and all eternity.
The doctrine of eternal marriage is discarded by other religions by quoting Matthew 22:30; which reads, "For in the resurrection they neither marry nor are given in marriage, but are angels of God in heaven." By using this as their reference they fall in to the same error that the Sadducees fell into when they asked Jesus about the woman who married several men. In a way they acknowledged eternal marriage in asking " who's wife will she be in the resurrection?" This implies that there was a teaching at this time that married couples exist after our resurrection. Jesus then tells them that there will be no marriages after the resurrection. This is true, there will be no marriages performed after we are resurrected.
Eternal marriage is an ordinance that must be performed prior to this. Those who were not "sealed" by the priesthood before they are resurrected will go to one of the lower Kingdoms, (either the Terrestrial or Telestial) where they will be angels under God. That is why Jesus phrased it " no one shall marry or be given in marriage" at this time. It will be too late by then. It doesn't say, "there will be no husbands or wives." Just that no one can get married now.
This is why Jesus tells them in verse 29 that they do not understand the doctrine or the Power of God.
In the story of Job we read that after Job overcame his trials, God rewarded him by doubling all that he had before.
He went from 7000 sheep to 14000. Also, he went from 3000 camels to 6000 camels, etc. What about his children? Before all his children died he had 7 sons and 3 daughters. After the Lord blessed him for overcoming his trials, he was only given 7 sons and 3 daughters, not double of what he had before. Did God make a mistake, and forget to double his children like he did everything else? Of course not, we can interpret from this that his children had been "sealed" to him before they died. Therefore, having 7 sons and 3 daughters before, and then 7 sons and 3 daughters after the trials, his children were indeed doubled, since in the afterlife, they will still go on being his children for all eternity.