Hebrews 7:5

7:5 And those of the sons of Levi who receive the priestly office have authorization according to the law to collect a tithe from the people, that is, from their fellow countrymen, although they too are descendants of Abraham.

Hebrews 10:1

Concluding Exposition: Old and New Sacrifices Contrasted

10:1 For the law possesses a shadow of the good things to come but not the reality itself, and is therefore completely unable, by the same sacrifices offered continually, year after year, to perfect those who come to worship.

Hebrews 10:16

10:16 “This is the covenant that I will establish with them after those days, says the Lord. I will put my laws on their hearts and I will inscribe them on their minds,”