Deuteronomy 2:9

ואל תתגר בם וגו׳ AND DO NOT CONTEND WITH THEM [IN WAR] — As regards Moab He forbade them (the Israelites) only war against them, but they may frighten them, appearing before them when equipped for war; therefore it is written, (Numbers 22:3) "And Moab was afraid because of the people", because they took plunder and loot from them. But about the children of Ammon it is said, (v. 19) “Do not contend with them" — no provocation of any kind, — as a reward for the modesty shown by their ancestress, Lot's younger daughter, who did not publicly divulge regarding her father's conduct, as his elder daughter did, who called her son's name “Moab" (i.e. born of the father) (Bava Kamma 38b; see Rashi on Genesis 19:37). ער is the name of the district.

And the Lord said to me, Do not harass Mo᾽av, nor contend with them in battle: for I will not give thee of their land for a possession; because I have given ῾Ar to the children of Lot for a possession.

וַיֹּ֨אמֶר יְהֹוָ֜ה אֵלַ֗י אַל־תָּ֙צַר֙ אֶת־מוֹאָ֔ב וְאַל־תִּתְגָּ֥ר בָּ֖ם מִלְחָמָ֑ה כִּ֠י לֹֽא־אֶתֵּ֨ן לְךָ֤ מֵֽאַרְצוֹ֙ יְרֻשָּׁ֔ה כִּ֣י לִבְנֵי־ל֔וֹט נָתַ֥תִּי אֶת־עָ֖ר יְרֻשָּֽׁה׃