You shall love a convert, for you were convets in the land of
Egypt. (Devarim 10:19)
In addition to the mitzvah of loving all our fellow Jews, there is a
special mitzvah to love converts. Thus, we have a double mitzvah to love
a convert. The Sefer HaChinuch (mitzvah 431) teaches that a stranger in
town is like a convert and is therefore included in this mitzvah.
The Torah cautions us in thirty-six places to treat a convert properly
(Bava Metzia 59b). Whereas we are commanded to love all Jews "as
ourselves" (mitzvah 22), there is no limitation given to how much we
should love a convert (Rambam, Hilchos Dei'os 6:4). In addition, we are
taught that Hashem loves converts (Devarim 10:18), which means that
fulfilling this mitzvah is also a mitzvah of emulating Hashem.
There is no greater joy than causing happiness to the poor, orphans,
widows, and converts. (Rambam, Hilchos Megillah 2:17)