This post is dedicated in memory of Etya Sarah bat Yitzchak ha-Levi. May it be an aliyah for her neshama.
Many new immigrants who move to Israel are often met with astonishment from Israelis (and more than a few Americans) as to why they would leave the US to make a new life for themselves in Israel. Of course, there is something exciting about being part of the 'Start-Up Nation'. There are mystical reasons to live here: according to tradition, while the rest of the world was flooded in the mabul, no waters crossed over the boundaries of Israel, leaving the land and air here with the original qualities imbued with the whole world during creation. Related to this, the Jewish Sages say that just breathing the air of the land makes people wise and that Divine Intervention is felt more strongly here. Beyond good food, and holy air, many people actually move here for a more substantial reason: because it's a mitzvah.
There are different accounts of what all of the 613 mitzvot laid out in the Torah are, but almost everyone agrees living in the Land of Israel, Eretz Yisrael, is one of them. The source for this is in Bamidbar 33:53 which says, "...dwell in the land because I gave it to you". The famous Torah scholar and Kabbalist, the Ramban, expounds on this passuk, saying "It's better to live in Israel, even in a town that is mostly non-Jewish, than to live in the Diaspora in a Jewish town." Those are strong words.
Living in the land is considered so important that one needs a valid reason to even leave! There are three reasons given for why one is allowed to leave Eretz Yisrael: for parnassah (they can't make a living here), for shidduchim (to get married), and to learn Torah (if there is an opportunity for a better or safer place to learn, which was a valid reason for many years, but less so today).
Let us consider how special this mitzvah really is - it's one of only three that you do with your entire body (the other two being dwelling in the sukkah and mikvah). Basically, even if you are just taking a nap while in Eretz Yisrael, you are doing a mitvah. One of the mitzvot that are contingent upon being in the land is that every dalet amot you walk (about 8 ft), is a mitzvah. Just strolling down to the corner makolet (small supermarket) to get milk you are racking up those mitzvah points.
As mentioned before, there are certain mitzvot that only apply in Israel when a majority of the world's Jews live in the Land - such as many agricultural laws, the forgiving of debts, tithes given to Kohanim. In addition to the individual mitzvah of living in the land, these laws have a communal aspect - since the majority of Jews need to live here for them to be mitzvot, then it suddenly becomes everyone's responsibility to live here to help one another fulfill all the mitzvot. That is part of being a Jew - helping each other in life. So what are you waiting for? Come live here, help yourself, and your fellow Jew, do a mitzvah!