How could Avrohom have considered not burying Sarah in the ground?
(23,8) “If it be your will to bury my dead from before me, listen to me and intercede with Ephron the son of Tzochar.”
The Ramban writes that the explanation of the words “from before me” is that Avrohom said to them: If you do not do sell me a burial plot, then I will bury her in a coffin.
But this is a problem according to what the Ramban himself proves in his sefer Toras HaAdam from the conclusion of the gemora in Sanhedrin 46b, that according to the Torah the mitzvah of burying the dead can only be fulfilled by burying the body directly in the earth, and not by burying the body in a coffin which is included in the prohibition not to leave a body unburied overnight. But from his explanation of Avrohom’s statement it seems that one can fulfil the mitzvah of burial even in a coffin.
But it seems to me that we can explain it according to what I wrote elsewhere when explaining the posuk concerning Moshe’s death - “and no person knows his place of burial until this day” (Devarim 34:6) - that there are two reasons why we are required to bury the dead. The first we see from the Midrash on the posuk in Bereishis 3:19 when Hashem said to Adam HaRishon after he had sinned “With the sweat of your face you shall eat bread until you return to the ground, for from it you were taken; for dust you are, and to dust you will return”. Hashem said to him: The handful of earth from which you were created, is it not stolen property in your hand? The explanation of this Midrash is that man was created from the ground in order to rectify it and purify it so that it will become like the soul. But since Adam sinned and did not rectify the earth, he must return to the ground. And this is like returning a stolen article to its owner, as the Maharal of Prague explained.
And I remember that when I was young I heard my Rebbe from Socatchov explain with this the gemora in Chullin 92b, which says that one of the mitzvos which the Noachides still observe is that they do not weigh out the flesh of a dead person in the marketplace. But where do we see that Noachides are commanded not to eat a dead man’s flesh? The Rav from Socatchov answered that since the mitzvah to bury the dead in the ground is like returning a stolen article to its owner, someone who does not do so is stealing from the ground. Therefore, eating a dead man’s flesh is included in prohibition of stealing and Noachides are commanded not to steal.
And the sefer Toras HaAdam also brings the gemora which says that Rebbi commanded that when they bury him the coffin should have a hole in it. What he meant was that they should remove the bottom panel of the coffin and lay him on the earth because it is a mitzvah to bury in the earth. And this was not because the earth of Eretz Yisrael was so beloved to him, but rather it is true even outside of Eretz Yisrael, as it says “and to dust you will return”.
The second reason why we are required to bury the dead is given by the Tosafos Yom Tov in Pirkei Avos 2:7 in the name of the Kol Bo - because it is hard for the soul to see the body disgraced, lying around without burial.
The practical difference between these two reasons is if the body is buried in a coffin. According to the second reason he will have fulfilled the mitzvah of burial, since the body is not lying around in disgrace. But according to the first reason of returning a stolen article the body must be buried directly in the earth. The Ramban writes that even if the coffin is buried in the ground the mitzvah of burial is not fulfilled completely if it is a whole coffin.
Now, Moshe Rabbeinu was called a man of G-d, and was purified completely like an angel. Therefore burial in the earth was irrelevant to him since his body was no longer of the same type as the earth, and so there was no 'stolen article' to return. And this is the explanation of the posuk “and no person knows his place of burial”, because why did he need to be buried in the ground when it was sufficient to bury him in a coffin?
Now the explanation of the Ramban regarding the burial of Sarah is clear. Because Chazal taught that Sarah died without any sin, and thus she had rectified the material part of herself completely. Therefore her body no longer had any relationship to the ground, and so there was no 'stolen article' that needed returning. Thus according to everybody the Torah obligation of burial could be fulfilled by burying her in a coffin.
However, the gemora in Sanhedrin 46b learns that the Torah requires burial in the ground from the double expression כי קבור תקברנו - “but you shall surely bury him”. That is, if the Torah had only written קבור I would have thought that burial can be fulfilled with a coffin, and therefore it wrote the superfluous word תקברנו to teach that we require burial in the actual ground.
It seems to me that the reason why the gemora does not learn this from what Hashem said to Adam “until you return to the ground” is because we cannot bring a proof from the law of the Noachides before the giving of the Torah to the law of Yisrael after the giving of the Torah. Because the Torah was given to Yisrael in order to purify their material selves through the power of the Torah, and to make their earthly portion like the soul. (This is why Chazal taught that only Yisrael are called אדם (alluding to the fact that they came from the ground), since for Yisrael it is a worthy appellation, because even though that they are created from the ground, through the power of the Torah they can become purified like the angels. But this is not so by the nations, and so by them the name אדם would be a derogatory term, and therefore they are not to be called אדם). If so, there is good reason to think that after the giving of the Torah burial in the ground is not required, and so burial in a coffin would be sufficient to fulfil the reason given by the Kol Bo. Therefore, an extra word was needed to teach us otherwise.
In fact, the opinion of R. Chananel is that the mitzvah of burial, meaning the obligation to bury in the ground, is only a Rabbinic law. According to this opinion we have to say like we said above, that we can’t bring a proof from Adam HaRishon to what the law should be after the giving of the Torah, because it was given to Yisrael to elevate their material selves to the level of the soul, and therefore they do not indeed require burial in the ground according to the Torah.
And we can explain with this a puzzling Midrash on the posuk “The sea saw, and it fled” (Tehillim 114:3). What did it see? The coffin of Yosef. The commentaries had much difficulty with this Midrash, but we can explain it according to what the Sforno wrote on parshas Vayechi, that Yosef was buried in a coffin and not in the ground. His comment can be shown to fit with the gemora in Sotah 13a, which brings a dispute whether the the coffin was sunk in the River Nile or buried in the burial plot of the kings. Because certainly according to the opinion that it was sunk in the Nile burial in the ground was not fulfilled, but even according to the other opinion since it was a whole coffin made of metal the mitzvah of burial in the ground was not fulfilled.
And perforce the reason why he was not buried in the ground was because Yosef was a complete Tzaddik, and had rectified his material portion completely so that he no longer had any relevance to the ground. Thus, he was above nature and therefore nature had no right to block his way, and so when the sea saw him it fled from before him.