פּירוש אויף בראשית 14:20

אשר מגן WHO HATH DELIVERED [THY ENEMIES INTO THY HANDS] — מגן means who has handed over or surrendered, as (Hosea 11:8) “How shall I give thee over, (אמגנך) Israel”

ייתן לו, “he gave him;” Malki Tzedek gave Avram a tithe of everything. Our sages in Nedarim 32, interpret this verse as an allusion by the Torah to Malki Tzedek having forfeited his status of being G-d’s priest, and it being transferred to Avram, as he had committed the error of blessing a mortal human being, Avram, before blessing the immortal Lord. Avram himself had criticised Malki Tzedek for having mentioned him first in blessing both G-d and him. The latter accepted the reproof and treated Avram as the priest by tithing to him all that belonged to him. The Talmud cites a verse from Psalms: 110,4, as its source; there we read: נשבע ה' ולא ינחם אתה כהן לעולם על דברתי מלכי צדק, “The Lord has sworn and will not relent, You are a priest forever a rightful king by My decree.” [Rabbi Moshe Alshich explains there that G-d actually killed all the people Avram fought, as a priest who has killed does no longer qualify for priestly duties. Ed.]

AND HE GAVE HIM A TENTH OF ALL. Abraham did not wish to take for himself from a thread even to a sandal tie.²⁰²Verse 23 here. But the part of the Most High he set aside in order to give it to the priest. Now the king of Sodom went out to meet Abraham at the vale of Shaveh²⁰³Above, Verse 17. in his honor, and he accompanied him to the city of Salem where Melchizedek brought out bread and wine for the people that followed him. The king of Sodom did not ask anything of Abraham, but when he saw his generosity and righteousness in giving the tithe to the priest, then he also asked for the souls²⁰⁴The prisoners. Verse 21 here. by way of charity. Abraham, trusting that his G-d will give him riches, possessions and honor, did not wish to take anything from him, and so he returned all the wealth of Sodom which belonged to him, and all the wealth of Gomorrah for it to be returned to its owners. The king of Sodom had asked above all for the souls,²⁰⁴The prisoners. Verse 21 here. but Abraham’s consideration above all was that they should not say that they made Abram rich.²⁰²Verse 23 here. Now the other places mentioned²⁰⁵Admah, Zeboim and Bela. Verse 2. had been destroyed by the enemy in battle; only the wealth of Sodom and Gomorrah, among the cities of the five kings, fell into the hands of the enemy because since their kings were lost in the slime pits, their cities remained defenseless.²⁰⁶Hence the four kings were able to plunder Sodom and Gomorrah, and when Abraham recaptured it from them he restored it to its original owners. The other three cities (see preceding note) defended themselves and were completely destroyed in battle.
It is possible²⁰⁷Ramban is now suggesting that the four kings had taken plunder from the other three cities as well and that is alluded to in the verse, as will be explained. that [the plunder from the other three cities is alluded to] in the words of Abraham: “If from a thread even to a sandal tie²⁰²Verse 23 here. will remain with me of all the wealth that has come to me from all of you;²⁰⁸“From all of you,” i.e., from all the five cities. and if I take anything that is thine²⁰²Verse 23 here. of your wealth which you, the king of Sodom, gave me.”

ויתן לו AND HE — Abraham — GAVE HIM מעשר מכל A TITHE OF EVERYTHING that he had, because he was a priest.