"Techiyat HaMetim" - (f.); Revival or resurrection of the dead; one of the fundamental beliefs of the Jewish Religion, and the last of the RAMBAM's list of thirteen such beliefs (one source of this list is the set of "Ani Maamin"s at the end of "Shacharit," the Morning Prayer).
The Talmud asks, "What is the Biblical source for "Techiyat HaMetim?" And the somewhat enigmatic answer given is "Kal VaChomer MiChitah;" namely, that it follows by an "a fortiori" - type act of logic (that is, reasoning from a minor premise to a major premise) from the observable fact, assumed by the Bible when it refers to wheat, that wheat reproduces every year. One basis of this idea seems to be that just as the seed needs to disintegrate and decompose in order to produce new life, so does the human body. The reasoning seems to be, "if wheat can do it, certainly so can a human being!?"
One difficulty with this, at first glance, is that the only reason that wheat reproduces is that it has been replanted, without which act of kindness performed by the farmers, we would enjoy no bread. However, there is a Midrash that says that the nature of wheat will change at the time of the "Mashiach," such that it will not need to be replanted, in order to reproduce.
Another difficulty is that at least twice in the Bible, in the case of Eliyahu HaNavi, Elijah the Prophet, as recounted in "Melachim"/Kings I (17:22), and in the case of his disciple, Elisha HaNavi, as recounted in "Melachim" II (4:33-35), we find instances of human beings being given the ability to revive the dead! Why does the Talmud ignore these obvious cases of "Techiyat HaMetim" actually occurring in the Bible?
A possible response is that the Talmud was looking for a "natural" explanation of the phenomenon, miraculous though it does seem from our present perspective.
Basically, "Techiyat HaMetim" seems to be one of the necessary conditions for the fulfillment of HaShem's promise of "Sechar," Reward, for the Righteous in "Olam HaZeh," this World, as a prelude to their reward in "Olam HaBa," the World-to-Come.
Gitin, there is an account of four hundred boys and girls being transported by sea to serve the Roman troops in immoral ways at the time of the destruction of the Second
"Beit HaMikdash," or Holy Temple. The Talmud recounts how the girls considered jumping overboard to escape a fate worse than death. They asked their leader, "Will HaShem bring us back at the time of
"Techiyat HaMetim?" And the leader answered, "It is written 'I will bring back from
Bashan; I will bring back from the depths of the sea.' " Hearing that, the young women immediately threw themselves into the sea.
The gassed and cremated Jews of the Holocaust, whose remains are "nowhere to be found," will be gathered up miraculously by their Creator together with martyred Jews of all generations, in addition to all righteous gentiles, to be revived by the Creator, when that wonderful Day comes.