King James Version
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:English Standard Version
And those descendants of Levi who receive the priestly office have a commandment in the law to take tithes from the people, that is, from their brothers, though these also are descended from Abraham.New International Version
Now the law requires the descendants of Levi who become priests to collect a tenth from the people--that is, their brothers--even though their brothers are descended from Abraham.