Hebrews 7:5

Now the law commands the sons of Levi who become priests to collect a tenth from the people—that is, from their brothers—though they too are descended from Abraham.

And verily they that are of the sons of Levi, who receive the office of the priesthood, have a commandment to take tithes of the people according to the law, that is, of their brethren, though they come out of the loins of Abraham: