Commentary for Genesis 14:18

ומלכי צדק AND MELCHIZEDEK — A Midrashic explanation is that he is identical with Shem, son of Noah (Nedarim 32b).

AND MELCHIZEDEK KING OF SALEM. This is Jerusalem, just as it is said, In Salem is set His tabernacle.¹⁷³Psalms 76:3. In the days of Joshua, its king was also called Adoni-zedek.¹⁷⁴Joshua 10:1. Since time immemorial the nations knew that this place, which was the choicest of all places, is in the center of the inhabited region. Or perhaps they knew of its superiority by tradition, i.e., that it is exactly opposite the Heavenly Sanctuary, where the Divine Glory of the Holy One, blessed be He, who is called Tzedek (Righteousness) abides.¹⁷⁵This explains why the early inhabitants of Jerusalem called their king Malki tzedek, literally, “My king is righteousness.”
In Bereshith Rabbah¹⁷⁶43:6. [we find that Jerusalem is called Tzedek because] “this place makes its inhabitants righteous. And Melchizedek means ‘the lord of Zedek.’¹⁷⁷The Midrash is thus teaching that his name was not “Tzedek” but that he was the lord of a place called Zedek. Jerusalem is called Tzedek, as it is said, ‘Tzedek’ (Righteousness) lodged in it.”¹⁷⁸Isaiah 1:21.

הוציא לחם ויין, to all those returning from battle who were tired.