The seforim tell us that there is a bone in the body that never gets destroyed; it doesn’t receive sustenance from any food except food eaten at a Melave Malka seudoh. This is the bone G-d uses to start the process of Techiyas hameisim. It’s called ‘Luz’.
Now these are perplexing statements to say the least. What is this bone? Why does it not get any benefit from anything we eat, except the melave Malka? Why does G-d need this bone to start the techiyas hameisim process? What is the significance of it being called ‘Luz’ and what has it to do with techiyas hameisim?
It gets stranger. The Zohar Hakodosh informs us that this ‘bone’ Luz, has another name, בתואל הארמי - Besuel the sly one, and also,בת בתו של א-ל – the daughter of the daughter of G-d. So it’s called Luz and Besuel, and it’s the daughter of the daughter of G-d. Interesting.
There is a discussion in the Midrash as to what this bone is. There are those who say it is a small bone at the top of the spine, the size of a lentil. Others say it’s a clod of earth from the decomposed body [after death]. The Ari Hakodosh tells us a rule about such discussions in Midrash; there is never any disagreement; the Rabbis are merely presenting and expressing various facets of the same diamond, different views of the same thing.
Rabbi Aryeh Kaplan zt”l suggests that the ‘Luz bone’ is in fact the DNA of the person. Perhaps we can take this a step further and thus understand all the various statements of Chazal.
Rabbi Chaim Vital says the soul is attached to the finest part of the physical body. He further says that though there are levels in creation, e.g. human, animal, vegetable, mineral, the levels have an in-between stage, an interface. I suggest that there is an interface between the neshomoh and the body. There is something between the physical and spiritual, between even the DNA and the Neshomoh, that binds the soul to the body. This is the Luz ‘bone. It does not receive any nourishment from normal food because it isn’t physical. But it is nourished by the melave Malka because that meal represents the purpose of this ‘bone’.
What are we doing when we eat the melave Malka? What is its significance? During Shabbos we are in a higher spiritual realm. The Zohar HaKodosh calls the world of Shabbos, ‘the world of souls’. When we take leave of Shabbos and enter once again the six days of the week, we are re-entering the physical. And that is exactly what techiyas hameisim is, the rejoining of the soul with the physical.
Therefore, this ‘bone’ receives nourishment only and especially from the melave Malka. Chazal implied by that the true nature of this ‘bone’. Chazal say it is situated between the head and the spine meaning that it lies between the Neshomoh [which is often referred to as being in the head of a person] and the physical. It is called the daughter of the daughter of G-d because the Zohar always refers to the soul as the daughter of G-d: this ‘bone’ is a step removed from the soul, hence ‘the daughter of the daughter of G-d’. It is called בתואל הארמי - Besuel the sly one, because it lies between the physical and spiritual, neither completely one nor the other.
And therefore it is called Luz. Where do we find Luz mentioned in the Torah? What does it refer to? We find it mentioned in Parshas VaYaytsay and VaYishlach where Yaakov names a place originally called Luz, ‘Beis E-l’ – literally the House of G-d. That’s why the sages called this bone ‘Luz’, because it is our personal ‘Beis E-l’. This Luz is the House of our G-dly soul, the House of G-d.
May we merit to see Techiyas Hameisim. Enjoy your Melave Malkah.
 See Siddur Rav Yaakov Emden
 Beginning of Toldos
 Brought down many times by Rav Chaim Vital; see for example ’Mamar Pesiyos shel Avrohom Ovinu’.
 In an essay entitled ‘The Resurrection’.
 Sha’ar HaKedushoh