Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 2
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 2, with English translation by Maimonides (Rambam).
לְיַחֲדוֹ, שֶׁנֶּאֱמָר: "ה' אֱלֹהֵינוּ, ה' אֶחָד" (דברים ו, ד).
To unify Him, as [Deuteronomy 6:4] states: "God is our Lord, God is one."