9 And Hashem said to me: Do not harass the Moabites or provoke them to war. For I will not give you any of their land as a possession; I have assigned Ar as a possession to the descendants of Lot.—
va-YO-mer a-do-NAI ay-LAI al ta-TZAR et mo-AV v’-al tit-GAR BAM mil-kha-MAH KEE lo e-TAYN l’-KHA may-ar-TZO y’-ru-SHAH KEE liv-nay LOT na-TA-tee et AR y’-ru-SHAH
2:9 I have assigned Ar as a possession to the descendants of Lot
The people of Moab are descendants of Lot, nephew of Avraham. When Avraham went to Egypt to escape the famine, he told the Egyptians that Sara was his sister, instead of his wife, in order to save his life. The Sages of the Midrash explain that Lot, who was with them, maintained his silence and preserved the secret. As an expression of gratitude for this act of nobility, the children of Avraham are forbidden from attacking the children of Lot generations later, even for the purpose of expanding the borders of Israel.