וַיֹּ֣אמֶר הַגֹּאֵ֗ל לֹ֤א אוּכַל֙ לגאול־[לִגְאָל־] לִ֔י פֶּן־אַשְׁחִ֖ית אֶת־נַחֲלָתִ֑י גְּאַל־לְךָ֤ אַתָּה֙ אֶת־גְּאֻלָּתִ֔י כִּ֥י לֹא־אוּכַ֖ל לִגְאֹֽל׃
האָט דער אױסלײזער געזאָגט: איך קען עס ניט אױסלײזן פֿאַר מיר, װאָרום איך װעל נאָך פֿאַרדאַרבן מײַן אײגענע נחלה. לײז דיר דו אױס װאָס איך דאַרף אױסלײזן, װאָרום איך קען ניט אױסלײזן.
Rashi
For I would mar my own inheritance. נַחֲלָתִי =] my offspring, as in, “the inheritance of Adonoy is children;”4Tehillim 127:3. to give my offspring a stigma, for it is stated, “Neither an Ammonite nor a Mo’avite may enter [into Adonoy’s community],”5Devarim 23:4. but he erred [by not interpreting it as] “an Ammonite but not an Ammonitess.”6He was not aware that the Torah prohibited only the male Mo’avites from entering the ranks of Bnei Yisroel, but the females were permitted. Alternatively, he knew that females were permitted to enter the ranks of Bnei Yisroel, but he feared that in future generations the ruling may be challenged, as it was in Dovid’s time by Do’eg.
Ibn Ezra
"Lest I ruin my own inheritance." He had a large estate. And some say it hints at his wife.
Ibn Ezra
"Redeem it for yourself." Here, I have given you the authority, for I cannot do it.