Tosefta for Menachot 123:4

The first Passover was [divided] among three groups (כתות not בתים, see GR"A and Pes. 5:7) and the second Passover was not [divided] among three groups. A Tamid sacrifice would be slaughtered in the evening, he (i.e., the Kohen) would burn the incense, and he would tend to the candles [of the menorah]. He would come to where the Passover offering was located, and he would cut it open and take out its sacrificial portions, even four or five [offerings at a time]. He would put them on a tray and burn them on top of the Altar. And on the Sabbath he would keep the carcass "dressed" (i.e., not flayed) and leave it and go out. Rabbi Yishmael bar Rabbi Yochanan ben Berokah says, [if] the fourteenth [of Nissan] fell on the Sabbath, he would not flay [the carcass] except until the place of the waving (i.e., the breast and thigh, see Men. 62a:1). [If] the Kohen who was to offer [the sacrifice] on the Altar would pour out [the blood] in a single pouring against the base [of the Altar], it would be disqualified. The Levites would stand on their platform and finished the Hallel in song. If they finished it, they would repeat it, and if they repeated it, they would repeat it a third time, although [in actuality] they never repeated it a third time in all their days. Said Rabbi Yehuda -- "in all their days" -- [indeed,] the third [and last] group never reached to "I love the Lord, for He hears" (Ps. 116:1), because the people were few and they would call it the "lazy group."