In the second chapter of the Shema, which we recite each morning and evening, we repeat G-d's warning that turning away from Him to worship idols will result in being exiled from the Land which He has given us. This is immediately followed by the commandments of tefillin and mezuzah.
This connection is explained by the Midrash (Sifri Parshas Eikev) with a parable:
A king became angry with his wife and sent her off to her parents' home. As he banished her he instructed her to continue wearing her royal jewelry even while she was away so that she would be familiar with them when she eventually returned to his palace.
In similar fashion G-d instructed His beloved people as He banished them from His palace, the land of Israel, to continue being distinguished with their mitzvot so that they would be familiar with them when they returned.
Tefillin and mezuzah are mitzvot that are not dependent on living in the Land of Israel, unlike the many mitzvot relating to agriculture, and they are as incumbent on a Jew outside of Eretz Yisrael as upon one in the Land. Why then is this connection made between these mitzvot and the Land?
The answer lies in the unique spiritual status of Eretz Yisrael, which is directly ruled over by G-d, without the involvement of angels or any other entities. Mitzvot fulfilled in Eretz Yisrael, therefore, have the ultimate spiritual quality, while those fulfilled outside of the Land are of only “secondary” quality. This is communicated in the statement of our Sages (Sifri, Re'eh) that living in Eretz Yisrael is equivalent to all the mitzvot of the Torah. This unique status of Eretz Yisrael is also expressed in the Land's sensitivity to sin. The Torah warns us that Eretz Yisrael is not like other lands, and it will vomit out those who contaminate it (Vayikra 18:25). When the Kuttim (later known as the Samaritans) were brought to Eretz Yisrael by the Assyrian conqueror Sancheriv to replace the Ten Tribes he had exiled, they continued to worship idol. In response, G-d sent lions to devour them (see Melachim II chapter 17). In their native land they were not punished in such swift fashion, but Eretz Yisrael cannot tolerate idolatry.
G-d sanctified the nation dwelling in His land by commanding them mitzvot, and warned them that if they contaminate this Land with idolatry or licentiousness the land would vomit them out.
"Love of the Land" is therefore not expressed by merely mouthing patriotic slogans. Rather, by maintaining a standard of loyalty to G-d's Torah and living according to the moral standards set by the Torah, G-d grants us the privilege of remaining in our beloved Land with security and sanctity.
Adapted from Nachmanides’ Commentary on Vayikra 18:25