Ezra 7:24
Also we certify you, that touching any of the priests and Levites, singers, porters, Nethinims, or ministers of this house of God, it shall not be lawful to impose toll, tribute, or custom, upon them.
Ezra 8:17
And I sent them with commandment unto Iddo the chief at the place Casiphia, and I told them what they should say unto Iddo, and to his brethren the Nethinims, at the place Casiphia, that they should bring unto us ministers for the house of our God.