The Levites were an Israelite tribe whose male members had priestly duties. The tribe was descended from Levi, the third of the 12 sons of Jacob (Israel). The firstborn of all Israelites were supposed to be offered to the service of God. However, the firstborn of other tribes turned from God to worship the golden calf. Thus the priestly duties were assigned to the Levite tribe (Numbers 8:18; 18:7). At times during the period of Judges, men of other tribes acted as priests as well. But in the period of the kings, sacerdotal functions seem to have been carried out only by Levites. At this time, theoretically at least, all male Levites could act as priests.
Some time prior to the Babylonian Exile, however, a distinction was made between those Levites who actually served as priests and those who merely assisted. All priests were supposed to be Levites descended from Aaron, brother of Moses (Exodus 28:1). By the time of the Second Temple, there were three priestly orders: High Priest (Kohen), Priests (called sons of Aaron), and Levites. Levites, the lowest order, were not allowed to approach the Holy of Holies in the Temple. The Levites were divided into three groups according to descent from the sons of Levi: Gershon, Kohath, and Merari. Before a Levite was installed in the Lord's service he was bathed and shaved. Sacrifices were offered and the ceremony of the laying on of hands was performed (Numbers 8:5-13).
The duties of the Levites changed from time to time during the wanderings of Israel, but they generally included carrying the Ark, guarding the sanctuary, and caring for sacred vessels and offerings. Moreover, the Levites acted as teachers, administered justice, and assisted in the conduct of public worship, particularly as musicians (Numbers 3:5).
Their income came from a tithe collected from the other Israelites.
Unlike the other tribes, the Levites were given no fixed land on which to live. When Canaan was divided among the tribes of Israel, the Levites were scattered in townships throughout Israel, acting as teachers in addition to their other functions. They were allotted 48 cities throughout Israel, including 8 "cities of refuge" (Numbers 35:1-8).
After the Temple was built in Jerusalem, the priesthood was limited to the descendants of Aaron, while other Levites were given such duties as Temple maintenance.