Positive commandment · Mitzvat Aseh #34 of 613
To carry the ark upon our shoulders when it is to be carried
לשאת הארון על הכתף כשנושאין אותו
The verse · Bamidbar 7:9
וְלִבְנֵי קְהָת לֹא נָתָן כִּי־עֲבֹדַת הַקֹּדֶשׁ עֲלֵהֶם בַּכָּתֵף יִשָּׂאוּ
“But to the sons of Qehat he gave none: because the service of the sanctuary belonged to them; they bore it on their shoulders.”
The Rambam’s words
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."
לשאת הארון על הכתף כשנושאין אותו, שנאמר: "בַּכָּתֵף יִשָּׂאוּ" (במדבר ז, ט).
Why · Sefer HaChinuch #379
Carrying the Ark on the shoulder
“It is from the roots of the commandment that it is because the main glory of Israel is the Torah, through which they were made distinct from the other peoples and made into the portion of G-d.”
Who & when
“And this commandment is practiced at the time when Israel is on their Land; for there was a need then to carry the Ark of the Covenant of G-d because of war or when the king commanded.”
Where in the Mishneh Torah
Hilchot Vessels of the Sanctuary and Those Who Serve Therein הלכות כלי המקדש והעובדין בו