Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 140
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 140, with English translation by Maimonides (Rambam).
למנות שני יובל שנים ושמיטים, שנאמר: "וספרת לך, שבע . . ." (ויקרא כה,ח).
To count the years of the Jubilee year and the shemitah years within it, as [Leviticus 25:8] states: "And you shall count seven shemitah years."