Rashi on Genesis 14:20/רש"י על בראשית י״ד:כ׳

1אשר 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”

2ויתן לו AND HE — Abraham — GAVE HIM מעשר מכל A TITHE OF EVERYTHING that he had, because he was a priest.