Josephus Antiquities of the Jews 1.10.2
2 So Abram, when he had saved the captive Sodomites, who had been taken by the Assyrians, and Lot also, his kinsman, returned home in peace. Now the King of Sodom met him at a certain place, which they called The King’s dale, where Melchisedeck, King of the city Salem, received him. That name signifies, The righteous King: and such he was without dispute; insomuch that, on this account, he was made the Priest of God. However, they afterward called Salem Jerusalem. Now this Melchisedec supplied Abram’s army in an hospitable manner, and gave them provisions in abundance: and as they were feasting, he began to praise him, and to bless God for subduing his enemies under him. And when Abram gave him the tenth part of his prey, he accepted of the gift. But the King of Sodom desired Abram to take the prey; but intreated that he might have those men restored to him whom Abram had saved from the Assyrians, because they belonged to him. But Abram would not do so; nor would make any other advantage of that prey, than what his servants had eaten: but still insisted that he should afford a part to his friends that had assisted him in the battel. The first of them was called Eschol, and then Enner, and Mambre.
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