“In this self-subordination of Abram to Melchizedek there was the practical prediction of a royal priesthood which is higher than the priesthood entrusted to Abram’s descendants, the sons of Levi, and foreshadowed in the noble form of Melchizedek, who blessed as king and priest the patriarch whom God had called to be a blessing to all the families of the earth. The name of this royal priest is full of meaning: Melchizedek, i.e. King of Righteousness. Even though, judging from Josh. X.1, 3, where a much later king is called Adonizedek, i.e. Lord of Righteousness, this name may have been a standing title of the ancient kings of Salem, it no doubt originated with a king who ruled his people in righteousness, and was perfectly appropriate in the case of the Melchizedek mentioned here. There is no less significance in the name of the seat of his government, Salem, the peaceful or peace, since it shows that the capital of its kings was a citadel of peace, not only as a natural stronghold, but through the righteousness of its sovereign; for which reason David chose it as the seat of royalty in Israel; and Moriah, which formed part of it, was pointed out to Abraham by Jehovah as the place of sacrifice for the kingdom of God which was afterwards to be established. And, lastly, there was something very significant in the appearance in the midst of the degenerate tribes of Canaan of this king of righteousness, and priest of the true God of heaven and earth, without any account of his descent, or of the beginning and end of his life; so that he stands forth in the Scriptures, ‘without father, without mother, without descent, having neither beginning of days nor end of life.’ Although it by no means follows from this, however, that Melchizedek was a celestial being (the Logos, or an angel), or one of the primeval patriarchs (Enoch or Shem), as Church Fathers, Rabbins, and others have conjectured, and we can see in him nothing more than one, perhaps the last, of the witnesses and confessors of the early revelation of God, coming out into the light of history from the dark night of heathenism; yet this appearance does point to a priesthood of universal significance, and to a higher order of things, which existed at the commencement of the world, and is one day to be restored again. In all these respects, the noble form of this king of Salem and priest of the Most High God was a type of the God-King and eternal High Priest Jesus Christ; a thought which is expanded in Heb. Vii. on the basis of this account, and of the divine utterance revealed to David in the Spirit, that the King of Zion sitting at the right hand of Jehovah should be a priest for ever after the order of Melchizedek (Ps. Cx. 4).”
-C.F. Keil and F. Delitzsch, Commentary on the Pentateuch.