Numbers 8:23-26

23Then the Lord spoke to Moses again and he said,

24‘These are the rules about the Levites: The men who are 25 years old or older must go in to work in the Tent of Meeting.

25But they must stop that work when they are 50 years old. And they must not do that work after that.

26But they can help the other Levites in the Tent of Meeting. They can help them to do their jobs. But they themselves must not have any jobs. Those are the rules about the Levites and about their jobs.’