Hebrews 7

Note that the tithe, giving 10% of your income, is mentioned here, coming from what Abraham did in thanksgiving. The point of the beginning of chapter 7 is to show that Melchizedek had to be greater than Abraham since Abraham gave thanks to him. Jesus is like Melchizedek (remember, the author is writing to Jews who became Christian and uses Old Testament images as a result to prove his/her point) but more! Other priests come and go. Jesus lives forever. No need for a new one. Jesus intercedes for us forever.