Parashas Va'eira records the births of Lot's two sons, the forebears of the nations Amon and Moav. Centuries later, when the Jewish people left Egypt and passed by the lands of these two nations on their way to Eretz Yisrael, they refused to offer the Jewish people food and drink and Moav even hired Bilaam to destroy them (see also Ramban). This cruel conduct bore evidence of the faulty character of Amonite and Moavite men, but not of the women, because it is not the way of women to go out and bring refreshments for wayfarers (Yevamos 76b). As a result, the Torah commands us in Parashas Ki Seitzei not to allow the male members of these nations to marry into our people, even if they convert. Moreover, while we are usually required to seek peace with other nations, we may not accord this merciful treatment to Amon and Moav. Sefer HaChinuch explains that their cruel conduct revealed them as being despicable in the core and undeserving of our mercy. These Mitzvos thus educate us about the importance of kindness and compassion.

If we explore the history of Amon and Moav, we gain further insight into these Mitzvos. Lot was an orphan; his father Haran died in Ur Kasdim. His illustrious uncle Avraham took him under his wing and shared with him the good fortunes which he merited on account of his righteousness. When Lot's city was conquered by an axis of world powers, Avraham came to rescue him; when his city Sodom was overturned, it was only in Avraham's merit that he survived. Lot's descendants Amon and Moav are not only at fault for lacking compassion, but also for repaying with cruelty the immense kindness that the forebear of the Jewish people dealt to their ancestor (Ramban and Bechor Shor). The Torah refers to an ungrateful person as a naval, a despicable person (Devarim 32:6). Indeed, someone lacking the sensitivity to even recognize the kindness of others is surely rotten at the core. In contrast, the great men of our nation are well-known for possessing a fine sense of gratitude to others, and above all, to Hashem.

The ungrateful streak of Amon and Moav would continue for all generations; the Sages call them "the bad neighbors of Yerushalayim." They relayed to Nevuchanetzar that the Jewish prophets were predicting the destruction of Yerushalayim and urged him to come and conquer it, and they gleefully joined his forces (Sanhedrin 96b).

If we ponder the matter at its roots, it appears that the irreversible spiritual blemishes of these two nations began from the time of their conception. When Sodom and its sister cities were destroyed, Lot's daughters, thinking that the entire world had been destroyed, had an incestuous union with their father to perpetuate mankind, for the same reason Kain and Hevel were allowed to marry their sisters. Lot, though, had been told by the visiting angels that only that region would be destroyed, and he knew good and well that there was no such permissibility. The Gemara (Horayos 10b) remarks about this act of incest that it was considered virtuous for Lot's daughters and at the same time shamefully sinful for Lot. Amon and Moav emerged from those unions. Since only the male participant in those unions sinned, the male descendants would emerge blemished and forbidden from entry into the Jewish people, while the female descendants would emerge pure (Rabbeinu Avigdor HaTzarfati to Horayos ibid.). Indeed, the entire Davidic dynasty, including the Mashiach, emerged from Rus, a Moavite woman.

The above-stated law, that the ban against marrying Moavites is limited to male Moavites, is an oral tradition, which was a matter of dispute when Rus converted and Boaz sought to marry her. Boaz eventually did so, with the consent of the Beis Din of Beis Lechem. Rav Shlomo Alkabetz wrote a commentary to Megillas Rus called Shoresh Yishai. In his introduction, he suggests that this Megillah was written in order to publicize the authenticity of this oral tradition, which was necessary to legitimize the Davidic dynasty. Based on what we have written above, we may add that Megillas Rus substantiates the ruling of the Beis Din of Beis Lechem by describing the kindness and compassion of Rus in detail, thus demonstrating that the cruelty that characterizes Moav is clearly not shared by its female members.

It emerges that the moral sensitivities are largely dependent on the pureness of the soul and on spiritual genes that pass on from generation to generation. That is why it is strictly forbidden to mix the pure seed of Avraham, in whose spiritual genes are embedded kindness, compassion, and bashfulness (Yalkut Shimoni §82), with the impure seed of Lot's male descendants.

In closing, it is fascinating to note that Avraham himself eventually decided to separate himself from Lot upon observing his twisted values (see Panim Yafos to Bereishis 13:9). The impure roots of Amon and Moav had sprouted forth even before they were born.