"And when your brother becomes poor" (Leviticus 25:25) — these are Israel, as it is said, "And they were brought low through their iniquity" (Psalms 106:43). "And sells some of his possession" — for they were sold into the hand of Media, into the hands of Haman. "Then his redeemer shall come" — this is Mordecai. "And he shall redeem what his brother sold" — for he covered over the iniquities of Israel, since they were all deserving of slaughter, because they had eaten from the cooked foods of the star-worshipers, as it is said, "And when these days were fulfilled, the king made for all the people, etc." (Esther 1:5). And Haman incited himself against them, as it is said, "He cast pur, etc." (Esther 3:7). And by the merit of Mordecai they were saved, as it is said, "And it was overturned, etc." (Esther 9:1). Thus, "And he shall redeem what his brother sold."
When Your Brother Becomes Poor - Mordecai Redeems Israel from Haman
Midrash Tanchuma Buber, Behar 9:1
וכי ימוך אחיך, אלו ישראל, שנאמר וימוכו בעונם (תהלים קו מג), ומכר מאחוזתו, שנמכרו ביד מדי, בידי המן, ובא גואלו זה מרדכי, וגאל את ממכר אחיו, שכיסה עונותיהם של ישראל, שכולם היו ראויין להריגה, שאכלו מתבשלישי עובדי כוכבים, שנאמר ובמלאת הימים האלה עשה המלך לכל העם וגו' (אסתר א ה), ונתגרה בהם המן, שנאמר הפיל פור וגו' (שם ג ז), וזכות מרדכי נצולו, נאמר ונהפוך הוא וגו' (שם ט א), הוי וגאל את ממכר אחיו.