Hebrews 7: 1 - 3, 15 - 17
1 For this Melchiz'edek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him;
2 and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace.
3 He is without father or mother or genealogy, and has neither beginning of days nor end of life, but resembling the Son of God he continues a priest for ever.
15 This becomes even more evident when another priest arises in the likeness of Melchiz'edek,
16 who has become a priest, not according to a legal requirement concerning bodily descent but by the power of an indestructible life.
17 For it is witnessed of him, "Thou art a priest for ever, after the order of Melchiz'edek."

EWTN