Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 34
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 34, with English translation by Maimonides (Rambam).
לשאת הארון על הכתף כשנושאין אותו, שנאמר: "בַּכָּתֵף יִשָּׂאוּ" (במדבר ז, ט).
To carry the ark upon our shoulders when it is to be carried, as [Numbers 7:9] states: "And they shall carry it on their shoulders."