The Epistle to the Hebrews, the authorship of which has been long debated, urges the Hebrew Christian community not to fall back into Judaism.

Hebrews 7

7:5 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: