Parshat Ekev tells of the special mitzvah to love converts. Converts hold a special status in Jewish life, since they did the heroic deed of leaving their familiar surroundings, and casting their destiny with the Jewish people.
Many of our greatest ancestors - Abraham, Sarah, Rebecca, Rachel - were all converts! Also the great Talmudic sages Shemaya and Avtaliyon were converts. As was Onkelos, who wrote the Aramaic translation that is printed in virtually every Hebrew Bible.
So why does the Torah require us to be especially nice to converts? The commentators explain that a born Jew has relatives who will defend him; the convert does not, and that makes him particularly vulnerable.
On a deeper level, though, God Himself protects the convert directly. That's why this parsha says to love the convert "because you were strangers in the land of Egypt." Just as the Almighty guarded us and rescued us in Egypt, so too God defends the convert.
There is a fascinating kabbalistic idea that converts already have a Jewish soul, and even stood with the Jewish people at Mount Sinai. It is said that although the non-Jewish nations originally rejected the Torah, individual members of those nations sought to accept it. And the souls of these individuals appear in every generation as converts.
By the way, this idea of "future converts being present at Mount Sinai" helps explain why one of the primary requirements for conversion to Judaism is a commitment to keep the 613 mitzvot - just as the Jews did at Mount Sinai.