Hebrews 7:4-7

You realize just how great Melchizedek is when you see that Father Abraham gave him a tenth of the captured treasure. Priests descended from Levi are commanded by law to collect tithes from the people, even though they are all more or less equals, priests and people, having a common father in Abraham. But this man, a complete outsider, collected tithes from Abraham and blessed him, the one to whom the promises had been given. In acts of blessing, the lesser is blessed by the greater.