Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 207
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 207, with English translation by Maimonides (Rambam).
לאהוב את הגר, שנאמר: "ואהבתם את הגר" (דברים י, יט).
To love a convert, as [Deuteronomy 10:19] states: "And you shall love a convert."