Bikkurim, Chapter 3, Mishnah 2. Our Mishnah opens with a description of how the bikkurim were actually brought up to the Beis HaMikdash: "Keitzad ma'alin es habikkurim" - in what manner did they bring the bikkurim up to the Beis HaMikdash.
Background: the division of the nation into mishmaros and ma'amados:
The Mishnah begins by describing the arrangement that was in place in Eretz Yisrael, and the way things were divided geographically. Besides the groups of Kohanim and Leviim who would go up to the Beis HaMikdash, it is known that the Kohanim were divided into twenty four mishmaros - twenty four groups, each of which spent one week at a time performing the service in the Beis HaMikdash. Alongside them were the anshei ma'amad, Israelites who were present at the offering of the communal sacrifices: the daily offerings and the musaf offerings brought on Shabbos, Yom Tov and the like.
The anshei ma'amad were likewise divided into parallel groups, similar to a division into districts, each with a central city. One city was considered the primary city of that ma'amad, and all the various villages belonging to that ma'amad would gather to it.
The gathering and lodging in the city street:
"Kol ha'ayaros shebama'amad mizkanesos le'iro shel ma'amad" - all the towns and villages of that ma'amad, of that group, would assemble together in the central city, in the principal place of the ma'amad.
"V'lanin birchovah shel ir" - on the night before they set out on their journey they would sleep in the main street of that city.
"V'lo hayu nichnasin labatim" - they would not enter the houses, out of concern that there might be tumas ohel there: the possibility that a corpse, or part of one, was buried somewhere in the house, and remaining under that roof would cause tumah. For that reason, as an added precaution, they slept outside.
The call of the appointed officer in the morning:
"Lamashkim hayah hamemuneh omer" - in the morning the appointed officer, the head of the ma'amad, would announce in the words of the verse in Yirmiyahu: "Kumu v'na'aleh Tziyon el Hashem Elokeinu" - let us arise and go up to Tziyon, to the Beis HaMikdash, to Hashem our God. With this call the entire process would begin.
In summary: in this Mishnah we learned the opening stage of the procedure for bringing up the bikkurim: the gathering of all the towns of the ma'amad to the central city, the lodging in the city street out of concern for tumas ohel, and the call of the appointed officer at daybreak, "Kumu v'na'aleh Tziyon el Hashem Elokeinu" - the call that opened the journey to the Beis HaMikdash.