Parshat Ki Teitzei includes a prohibition upon the members of the nations of Ammon and Moav to marry Jewish women. The Torah states the reason for this prohibition explicitly: “Al Devar Asher Lo Kidemu Etchem BaLechem UVaMayim BaDerech BeTzeitchem MiMitzrayim,” “due to the fact that they did not greet you with bread and water on the way when you let Egypt” (23:5). Rashi, quoting the Sifri on the words “Al Devar,” offers another reason for this prohibition: “Al HaEitzah SheYaatzu Etchem LeHatiachem,” “because of the advice that they advised you to cause you to sin” (i.e. the Bnot Moav’s enticement of the men of Bnei Yisrael). The Siftei Chachamim explains that the Sifri was bothered by the apparently superfluous word “Devar,” as the word “Asher” alone (“Al Asher Lo Kidemu...”) would have conveyed the same message. “Devar” connotes Dibbur, speech, which leads the Sifri to the conclusion that the words that the Benot Moav used to lure Bnei Yisrael to sin certainly played a role in the reason for this prohibition.
The Keli Yakar is bothered by the fact that the Sifri finds a new reason for the prohibition when the Pasuk states explicitly that it is because they mistreated us so in the Midbar. If the prohibition is actually due to their causing Bnei Yisrael to sin, then why did the Pasuk not say so?
The Keli Yakar explains that the reasons of the Pasuk and the reason of the Sifri are really one and the same. The male members of Ammon and Moav intentionally did not bring bread and water so that Bnei Yisrael would be so hungry and thirsty that they would be willing to eat and drink anything – even meat and wine that had been offered to idols. The Dibbur of the women would not have lured Bnei Yisrael had they had the bread and water that they needed. It was the Moavi and Ammoni men, therefore, who were ultimately responsible for the transgressions of the Jews.