Hebrews 7:1-3 For this Melchisedec, king of Salem, priest of the most high God, who met Abraham returning from the slaughter of the kings, and blessed him; To whom also Abraham gave a tenth part of all; first being by interpretation King of righteousness, and after that also King of Salem, which is, King of peace; Without father, without mother, without descent, having neither beginning of days, nor end of life; but made like unto the Son of God; abides a priest continually.
The twofold purpose of Paul: [1] To show that Jesus Christ was the Person prophesied of in Psalms 110:1-7, which psalm the Jews uniformly held to refer to the coming Messiah. [2] To answer the objections of the Jews against Christ’s priesthood because He did not come from priestly stock and could not be the antitype of Aaron or fulfil Leviticus 21:10-15. From the Jewish viewpoint, Christ would be further disqualified because (1) No proselyte could be a priest; (2) No slave could be a priest; (3) No bastard could be a priest (Jews accused Him of being illegitimate); (4) No son of a Nethinim (temple servant of the priest) could be one; (5) No man whose father exercised a base trade such as the carpenter trade. Many Jews considered Him unfit to be a priest because of this.
Here Paul shows that the priest didn’t need to come from a particular stock, for Melchizedek was a priest of the most high God and not from Abraham or Aaron: He was a Canaanite. Jews considered any person not in the regular genealogies of Israel to be without a father and descent or genealogy. Then, too, Jews considered Melchizedek to be without a father and mother because he was a righteous man and should not be classed with the heathen. This special phraseology was not uncommon when a person was unknown or obscure. Such was their way of signifying that the parents were unknown.
‘Tenth part of all’ – It was customary among ancient nations to give a tenth of the spoils of war to the objects of their worship.

