Numbers 4:35 KJV
From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation:
Numbers 4:35, King James Version
In context
34 And Moses and Aaron and the chief of the congregation numbered the sons of the Kohathites after their families, and after the house of their fathers,
35 From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation:
36 And those that were numbered of them by their families were two thousand seven hundred and fifty.