Josephus Antiquities of the Jews 1.10.2
2 After rescuing the Sodomite captives, including Lot, Abraham came home in peace. The king of Sodom met him in the King’s dale, where Melchizedek, king of Salem (meaning “righteous king,” an apt title, for he truly was righteous) and also priest of God, welcomed him and his men generously, providing abundant provisions. As they dined, he praised Abraham and blessed God for subduing his enemies beneath him. After Abraham gave him a tenth of his spoils, Melchizedek gladly accepted. The king of Sodom requested that Abraham keep the loot but restore his citizens, and Abraham refused the reward, taking only what his men had already eaten, but still insisting his three friends—Eschol, Enner, and Mambre—take their rightful share.
1Q20 22
Genesis ApocryphonAbram camped in the valley of Shaveh, which is the valley of the king, the valley of Beth-ha-Kerem; and Melchizedek king of Salem brought out food and drink to Abram and to all the men who were with him. He was the Priest of the Most High God. And he blessed Abram and said, ‘Blessed be Abram by the Most High God, Lord of heaven and earth! And blessed be the Most High God who has delivered your enemies into your hand!’ And Abram gave him the tithe of all the possessions of the king of Elam and his companions. Then the king of Sodom approached and said to Abram, ‘My lord Abram, give me the souls which are mine, which you have delivered from the king of Elam and taken captive, and you may have all the possessions.’
Notes and References
"... Why, then, is the Talmudic discussion silent on the matter of Melchizedek’s circumcision? Given the thrust of the discussion, one might reasonably suggest that the text takes for granted that Melchizedek was indeed circumcised, in order to fulfil the priestly office. But then why does it emphasize instead the transfer of priesthood to Abraham? An explanation of this difficulty may, once more, originate in pre-Rabbinic attitudes to Melchizedek. Again, evidence from Qumran, this time in the shape of the Genesis Apocryphon from cave 1 (1Qap-Gen) provides assistance. (See D.A. Machiela, The Genesis Apocryphon (1Q20): A Reevaluation of its Text, Interpretive Character, and Relationship to the Book of Jubilees) This Aramaic ‘re-writing’ of episodes from Genesis certainly pre-dates the Christian era, and is intent on presenting Abraham as a sacrificing priest ..."
Hayward, Robert Targums and the Transmission of Scripture into Judaism and Christianity (pp. 384-385) Brill, 2010