ויבא הפליט. לְפִי פְשׁוּטוֹ זֶה עוֹג, שֶׁפָּלַט מִן הַמִּלְחָמָה, וְהוּא שֶׁכָּתוּב כִּי רַק עוֹג נִשְׁאַר מִיֶּתֶר הָרְפָאִים (דבר' ג') וְזֶהוּ נִשְׁאַר, שֶׁלֹּא הֲרָגוּהוּ אַמְרָפֶל וַחֲבֵרָיו כְּשֶׁהִכּוּ הָרְפָאִים בְּעַשְׁתְּרוֹת קַרְנַיִם, תַּנְחוּמָא וּמִדְרַשׁ בְּ"רַ זֶה עוֹג, שֶׁפָּלַט מִדּוֹר הַמַּבּוּל; וְזֶהוּ מִיֶּתֶר הָרְפָאִים, שֶׁנֶּאֱמַר הַנְּפִלִים הָיוּ בָאָרֶץ וְגוֹ' (לְעֵיל ו') וּמִתְכַּוֵּן שֶׁיֵּהָרֵג אַבְרָם וְיִשָּׂא אֶת שָׂרָה: ויבא הפליט AND THERE CAME THE ONE WHO ESCAPED — According to the real meaning this was Og who had escaped from the battle with the Rephaim (see Genesis 5:5) and it is to this that the text refers (Deuteronomy 3:11) “For only Og king of Bashan was left of the remnant of the Rephaim”, and this is what is meant by נשאר “left”, for Amraphel and his allies did not kill him when they smote the Rephaim in Ashteroth Karnaim. So is the statement in the Tanchuma 4:6:25 (Chukat). But according to the Midrash Genesis Rabbah (Genesis Rabbah 42:8) it refers to Og in allusion to him as the only one of the generation of the Flood who escaped that catastrophe, and this is what is meant (Deuteronomy 3:11) “of the remnant of the Rephaim”, for it is said. (Genesis 6:4) “The Nephilim (= Rephaim cf. Genesis Rabbah 26) were in the earth etc.” His intention in telling Abraham that his nephew was captured was that Abraham should wage war against the kings and that he should be killed so that he, himself, might marry Sarah.
העברי. שֶׁבָּא מֵעֵבֶר הַנָּהָר (בראשית רבה): העברי THE HEBREW — the one who came from the other side (עבר) of the River (Euphrates) (Genesis Rabbah 42:8).
בעלי ברית אברם. שֶׁכָּרְתוּ עִמּוֹ בְּרִית: בעלי ברית אברם CONFEDERATE WITH ABRAM (literally, owners of a covenant with Abram) — They had entered into a covenant with him. Other versions of Rashi have: another explanation is, they advised him to circumcise himself (to keep the [ברית] covenant), as is explained in another place (cf. Rashi on Genesis 18:1).