Later this morning I will be attending the temple with my father and many other family members. We will be taking the names of some of our ancestors that have not had the blessing of the fullness of the gospel during their life time.
John 3: 5
5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
In order to fulfill the law of God we go to the temple to do work for our ancestors, or ourselves.
For the living, we are washed and anointed as was commanded of the descendants of Aaron in Exodus, we make covenants with God and we accept a higher level of living such as keeping the law of chastity and so on. We also are married for eternity. Those having authority to bind on earth and in heaven, seal families together forever.
For those who have died, having not received of these blessings, we are baptized, confirmed with the Gift of the Holy Ghost, and go through each progression of covenants on behalf of them.
D&C 103: 9-10.
9 For they were set to be a alight unto the world, and to be the saviors of men;
Obad. 1: 21.
21 And saviours shall come up on mount Zion to judge the mount of Esau; and the kingdom shall be the Lord’s.
7 To open the blind eyes, to bring out the prisoners from the prison, and them that sit in darkness out of the prison house.
25 Verily, verily, I say unto you, The hour is coming, and now is, when the dead shall hear the voice of the Son of God: and they that hear shall live.
40 God having provided some better thing for us, that they without us should not be made perfect.
1 Peter 4
6 For for this cause was the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit.
15 And now, my dearly beloved brethren and sisters, let me assure you that these are principles in relation to the dead and the living that cannot be lightly passed over, as pertaining to our salvation. For their salvation is necessary and essential to our salvation, as Paul says concerning the fathers—that they without us cannot be made perfect—neither can we without our dead be made perfect.
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Here are some videos that show temples.