Hebrews 7:1-10 NIV
This Melchizedek was king of Salem and priest of God Most High. He met Abraham returning from the defeat of the kings and blessed him, and Abraham gave him a tenth of everything. First, the name Melchizedek means “king of righteousness”; then also, “king of Salem” means “king of peace.” Without father or mother, without genealogy, without beginning of days or end of life, resembling the Son of God, he remains a priest forever.
Just think how great he was: Even the patriarch Abraham gave him a tenth of the plunder! Now the law requires the descendants of Levi who become priests to collect a tenth from the people—that is, from their fellow Israelites—even though they also are descended from Abraham. This man, however, did not trace his descent from Levi, yet he collected a tenth from Abraham and blessed him who had the promises. And without doubt the lesser is blessed by the greater. In the one case, the tenth is collected by people who die; but in the other case, by him who is declared to be living. One might even say that Levi, who collects the tenth, paid the tenth through Abraham, because when Melchizedek met Abraham, Levi was still in the body of his ancestor.
NIV: New International Version