Rabbi Yakov Haber
Parshas Eikev ends with the verse, "Every place upon which the soles of your feet will tread will be yours: from the desert and the Lebanon, from the river, the Euphrates River, and until the western sea, will be your boundary" (Devarim 11:24).
On a simple level, the first half of the verse is limited by the boundaries delineated by the second half of the verse. Namely, Hashem is promising the Jewish people that everywhere they tread within the boundaries in Israel will become theirs. However, Chazal (Sifrei) understand the two halves of the verse as referring to two different concepts. Whereas the second half refers to the primary borders of the land, the first half describes the ability of the Jewish people to extend the original boundaries of the land and to endow the extension with the sanctity of the land of Israel. However, the ability to extend the land of Israel is contingent upon first conquering and sanctifying the land contained within the primary borders. Thus, the sanctification of the land is similar to an overflowing cup; the cup cannot overflow until it is first filled to capacity.
Our sages teach us that most of the mitzvos hateluyos ba'aretz did not apply until Yehoshua endowed the land with sanctity by conquering it (see Rambam Hilchos Terumos 1:2). This sanctity lapsed at the time of the Babylonian exile and was restored upon the resettlement of the land in the days of Ezra (ibid. 5). At first glance, this seems to imply that prior to Yehoshua's sanctification, the land of Israel did not possess kedusha. This, of course, presents many difficulties. Avraham Avinu was told by Hashem to travel to Eretz C'na'an and only left because of famine. Yitzchak Avinu was told to stay in the land. Ya'akov Avinu was promised by Hashem after his visit with Lavan that he would return to the land. Were the avos respectively promised to receive, commanded to stay in and return to a land without sanctity and uniqueness? Furthermore, many midrashim imply that Eretz Yisrael was chosen as a unique land at the beginning of creation (see e.g. Tanchuma, Pekudei 3 and Bemidbar Rabba 23:11). How can its sanctity be extended outside of its Biblical borders? How can a land not primordially endowed be given that endowment through human action?
Rav Eshtori HaParchi, an early authority who settled in Eretz Yisrael in the early 14th century, in his Kaftor VaFerach, a crucial early work on all matters concerning the Holy Land, explains these anomalies with a classic "Brisker" chiluk. There are two types of sanctity in the land of Israel. Hashem endowed the land with the first sanctity from the time of the avos. (Sha'arei Tzedek by the author of Chayei Adam views this sanctity as being present from the beginning of creation.) It is this sanctity that causes the Land to be the geographical location most conducive to fostering the closest connection to HaKadosh Baruch Hu. It is the root of the Land being the only one capable of housing the eternally holy city of Jerusalem and the Beis HaMikdash. It serves as the source of its exclusive ability to produce prophets, of being the portal of prayers to heaven, of having Torah study be more successful. The verse teaches in our parsha, "the eyes of Hashem are on it from the beginning of the year until the end of the year" (Devarim 11:12), informing us of its higher degree of Divine providence than in other lands. The Talmud (Ta'anis 10a) refers to all the lands of the world being nourished from the residue of the Land of Israel. It was in light of all of these unique qualities which existed even before the Jewish nation entered the Land, that the avos were promised this special unique land conducive to intense connection to their Creator.
But Eretz Yisrael has another sanctity as well, that which is relevant to the unique mitzvos hateluyos ba'aretz. It was this sanctity that Yehoshua and later Ezra bestowed upon the land. The former sanctity, in the language of the Chasam Sofer (Y.D. 234), is "kedushas olamim mimos olam ad sof kol yemos olam, lo nishtaneh v'lo yishtaneh - an eternal sanctity from the beginning of time until the end of time, it never changed and never will change". The second sanctity can and has lapsed through exile. (See Encylopedia Talmudit, Eretz Yisrael, sec. 2. for sources for all of the above, for further elaboration and for the important distinction between the first exile and the second exile.)
As can be expected, one sanctity can exist without the other. Before Yehoshua led the Jewish people into the Land, it possessed only the first, G-d-endowed, eternal sanctity, not the latter human-endowed sanctity. In effect, it was Eretz Yisrael with all of its unique spiritual qualities but without the obligation of mitzvos hateluyos ba'aretz. By contrast, if B'nei Yisrael would later conquer lands outside of Eretz Yisrael, they would be endowed only with the second type of sanctity. Produce growing there would be obligated in the mitzvos hat'luyos ba'aretz, but the lands would not contain the first sanctity. In effect, they would have the sanctity of Eretz Yisrael for mitzvos without actually being Eretz Yisrael. This was the status of>eiver haYardein where two and half tribes dwelled: It had the sanctity of Eretz Yisrael for mitzvos but, in effect, was not the Land of Israel. (See Birkei Yoseif 489 at length. Also see Nefesh HaRav (pp. 76-82) and Perach Mateh Aharon (Ahava), essays in the back, for Maranan Rav Yosef Dov and Rav Ahron Soloveitchik zt"l analyses of the two kedushos.)
Why did Hashem ordain two kedushos? Perhaps we can suggest that it was the Divine will that his beloved nation partner with him in bringing sanctity to the world in general and to Eretz Yisrael specifically. As the famous derasha asks on the verse, "asher bara Elokim la'asos - which Hashem created to do" (Bereishis 2:3): but Hashem had already created everything! What was left to do? La'asos was the charge to Man to take that which G-d had created and sanctify it further with his positive actions. Hashem endowed Eretz Yisrael to be the place where the most intense relationship with the Creator can be forged. All of the above-mentioned concepts: prayer, providence, and prophecy revolve around this and are provided "free of charge" by Hashem as a gift; we just have to access them. But B'nei Yisrael serve G-d with mitzvos; they even create more opportunities for mitzvos by endowing the land with the second degree of sanctity which, in effect, creates more mitzvos with which to serve the Creator.
This duality directly parallels the relationship of Shabbos and Yom Tov, shemita and yoveil (see Mesech Chachma beginning of Behar), and Torah shebichsav and Torah shebe'al peh; the former of each pair is totally created by Hashem, the latter has a distinct human component. The respective sanctities of Shabbos and shemita are fixed; the Written Law is fixed, undebatable and immutable. By contrast, the date of Rosh Chodesh and hence that of Yom tov is determined by beis din; the Sanhedrin counts the years to yoveil and declares its sanctity. The Torah shebe'al peh is rooted in the Divine principles received at Sinai, but their specific application is subject to human analysis and understanding. Perhaps the fact that land outside Eretz Yisrael can only achieve sanctity after the mainland is sanctified is indicative of the conceptual idea that only after total loyalty to Hashem's arena of sanctity is there room for human sanctification and creativity. (Also see Rav Sobolofsky's article, Holiness from Above and Below.)
In a sense, the entire chumash Devarim represents this partnership withHaKadosh Baruch Hu. Chachmei Yisrael analyze the precise interrelationship between Devarim and the first four chumashim. On the one hand, Devarim seems to be Moshe Rabbeinu's own review of the events of the Midbar and of the mitzvos of Hashem. The Gemara (Megilla 31b), noting the difference in phraseology between the tocheicha in parshas Bechukosai and that of parshas Ki Savo, states that the former was mipi haGevura, from the mouth of Hashem, whereas the latter was mipi atzmo, from Moshe's own mouth. On the other hand, Devarim contains new mitzvos as well which are clearly of Divine origin. Furthermore, the sanctity of chumash Devarim is equivalent in all ways to the other sections of the Torah. Derashos from which halachos are derived are made on verses in Devarim just as they are on verses from the other chumashim and carry the same halachic weight. Is Devarim then a Divine work or a human work? Abravanel states that originally Devarim was Moshe Rabbeinu's own "derasha", clearly Divinely inspired and based on everything he had learned and received prophetically from Hashem, but the words were his own. Afterward, Hashem commanded him to write down his speech with some modifications; it was at that time that Moshe's words became elevated to the status of Torah shebichsav. In effect, chumash Devarim originally had the status of Torah shebe'al peh and then, only after Divine re-dictation and Moshe's writing it down, did it become elevated to Torah shebichsav. This reflects the ultimate ability of lowly Man to partner with His Creator in elevating the world. The Jewish people not only develop new insights into the Torah, but its primary, first teacher's words actually became Torah shebichsav!
Rav Akiva Tatz in a recently given shiur quoted the first Tosfos in maseches Gittin that there is an allusion to the customary 12 lines of a get, a Jewish divorce document, in the Torah. There are four lines of space between each of the first four chumashim consisting of three gaps with four lines each for a total of 12. Why isn't the gap between Bemidar and Devarim counted as well? Rav Tatz suggested that the Torah represents connection between Hashem and the Jewish people and the gaps represent temporary separation which is the thrust of a get. But chumash Devarim, indicating as it does the ability of a human being to actually create Torah, is the ultimate testament to connection to Hashem. As such, the gap before Devarim is not included in the count of the lines of a get, the document of separation.
May our increased awareness of the dual sanctity of the Land of Israel and Hashem's great love of and confidence in the Jewish people to partner with Him guide us constantly in our lives.
 This was part of a derasha that was written by my father z"l which I delivered at my bar-mitzva several decades ago.
 Mori v'Rabi Rav C. Y. Goldwicht zt"l elaborated on this concept often as recorded in his Asufos Ma'arachos (e.g. Chanuka, Kocham shel Chachmei Yisrael).
 Vilna Gaon (recorded in the commentary to the Artscroll Stone Chumash, beginning of Devarim) interprets this Gemara differently. I believe that even according to his interpretation, there was still a need for an "elevation" of Moshe's words to become Torah shebichsav.