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; For this Melchisedec, king of Salem - See the whole of this history largely explained in the notes, See Genesis 14:18 (note), etc., and the concluding observations at the end of that chapter.
The name Melchisedec, מלכי צדק is thus expounded in Bereshith Rabba, sec. 43, fol. 42, מצדיק את יושביו matsdie eth Yoshebaiv, "The Justifier of those who dwell in him;" and this is sufficiently true of Christ, but false of Jerusalem, to which the rabbins apply it, who state that it was originally called Tsedek, and that it justified its inhabitants.
Salem is generally understood to be Jerusalem; but some think that it was that city of Shechem mentioned Joshua 20:7. St. Jerome was of this opinion.