“For Ḥeshbon was the city of Siḥon, king of the Emorites, and he fought against the first king of Moav, and took all his land from his possession, until Arnon” (Numbers 21:26). “For Ḥeshbon was the city of Siḥon” – this is what the verse said: “For the Lord loves justice” (Psalms 37:28). The Holy One blessed be He said to him: “Do not besiege Moav” (Deuteronomy 2:9), and Ḥeshbon was Moavite, as it is stated: “For Ḥeshbon was the city of Siḥon king of the Emorites, [and he fought against the first king of Moav and took all his land from his possession, until Arnon.]”
Israel came and took Ḥeshbon, which belonged to Siḥon, and everything that he had taken from Moav, as had they taken it from him, it would have been unjust robbery in their hand. Rather, Siḥon took it from Moav, and Israel from Siḥon; therefore, they were exempt from robbery. That is why it is written: “For Ḥeshbon was the city of Siḥon.” “Therefore, the allegorists will say: Come to Ḥeshbon.
The city of Siḥon will be built and established” (Numbers 21:27). “For a fire emerged from Ḥeshbon, a flame from the city of Siḥon; it consumed Ar of Moav, the lords of the high places of Arnon” (Numbers 21:28). “Therefore, the allegorists will say” – this is Bilam and his father, whom Siḥon hired to curse Moav, and they said: “The city of Siḥon will be built and established.… for a fire emerged from Ḥeshbon…it consumed Ar of Moav.” They cursed Moav that they would be delivered into his hand, “Woe to you, Moav” (Numbers 21:29).