Hebrews 7:5-15

5 And those descendants of Levi who are priests are commanded by the Law to collect one tenth from the people of Israel, that is, from their own people, even though they are also descendants of Abraham. 1
6 Melchizedek was not descended from Levi, but he collected one tenth from Abraham and blessed him, the man who received God's promises.
7 There is no doubt that the one who blesses is greater than the one who is blessed.
8 In the case of the priests the tenth is collected by men who die; but as for Melchizedek the tenth was collected by one who lives, as the scripture says.
9 And, so to speak, when Abraham paid the tenth, Levi (whose descendants collect the tenth) also paid it.
10 For Levi had not yet been born, but was, so to speak, in the body of his ancestor Abraham when Melchizedek met him.
11 It was on the basis of the levitical priesthood that the Law was given to the people of Israel. Now, if the work of the levitical priests had been perfect, there would have been no need for a different kind of priest to appear, one who is in the priestly order of Melchizedek, not of Aaron.
12 For when the priesthood is changed, there also has to be a change in the law.
13 And our Lord, of whom these things are said, belonged to a different tribe, and no member of his tribe ever served as a priest.
14 It is well known that he was born a member of the tribe of Judah; and Moses did not mention this tribe when he spoke of priests.
15 The matter becomes even plainer; a different priest has appeared, who is like Melchizedek.