Through recourse to Jewish traditions of interpretation, we discover that Melchizedek is identified in the Jewish Targums and midrashic sources as Shem, the first-born son of Noah. (Father Gadenz footnotes this as follows: footnote 14: Joseph Fitzmyer cites the Targum Neofiti I, the Fragmentary Targums, and the Targum Pseuto-Jonathan, all of which identify Melchizedek as Shem; see his article “Now This Melchizedek…’(Heb. 7, 1)’Catholic Biblical Quarterly
25 (1963), 313, fn. 32.) In this interpretation, the blessing by Noah of Shem-Melchizedek in Gen. 9:26 is understood as the patriarchal priestly blessing, which is then passed on by Shem_Melchizedek to Abraham in Gen. 14:19. Hence, Shem-Melchizedek, the first-born son of Noah, is the chief priest and patriarch (father figure) over his house, that is over all of his extended family which through ten generations includes Abraham as well (cf. Gen 11:10-26). Abraham, after receiving the blessing from Shem-Melchizedek, is designated to become the new chief priest and patriarch over all his descendants. (
Catholic for a Reason: Scripture and the Mystery of the Family of God, pp. 217-218).
Father Gadenz also notes that Saint Ephrem the Syrian, a fourth century doctor of the Church, and Saint Jerome, who studied under the Jews, also identified Shem as Melchizedek (St. Ephrem the Syrian
Commentary on Genesis section XI, in the
The Fathers of the Church, vol. 91 (Washington: The Catholic University of America Press, 1994), p. 151), and St. Jerome, Epistle 73
Patrologica Latina, vol. 22, 676-81). St. Jerome in his commentary on Genesis (Corpus Christianorum: Series Latina, vol. 72, 19), where in speaking of the Jews’ assessment of Melchizedek, writes:
They say that he [Melchizedek] was Shem, the son of Noah, and calculating the years of his life, they declare that he lived to the time of Isaac, and that all the first-born [from] Noah, until Aaron exercised the priesthood, were high priests (Catholic for a Reason: Scripture and the Mystery of the Family of God
, p. 218).
Scott Hahn, saying he is drawing upon Jewish Tradition, argues that it went without argument that Shem actually was Melchizedek. He argued that the early Christians assumed that was so, (as seen above by Sts. Jerome and Ephrem). Shem was the one blessed by Noah (Gen. 9:26). Noah was the Father, and priest, of all the earth. Thus, Shem received the blessing from Noah, and thus he now would be the priest over all the earth. That indeed shows how since Shem is priest-king, and would thus be a priest-king over all the earth, not just Salem. This shows even further how the type of the figure of Melchizedek (Which is a Title, not a Name, per se) is fulfilled in Jesus being a priest-king over all the earth (Scott Hahn, Tape series
The Epistle to the Hebrews 8 tapes, tape 3, St. Joseph Communications.) That is how he could be the source of blessing for Abraham, who would therefore accept it. That Melchizedek was Shem, is thus accepted by both Jewish and Christian traditions.