After describing the journey of the Israelites and their encampment adjacent to the Arnon ravine, several vague verses describe a certain event related to the Arnon ravine recorded in the “Book of the Wars of the Lord.” According to the Sages, it is a description of a miracle that transpired in the passages of the Arnon ravine, when the Emorites lay in wait to ambush Israel; but they themselves were killed.

“Therefore, it is said in the Book of the Wars of the Lord: Vahev by storm [et vahev besufa], and the tributaries of the Arnon, the outpouring of the streams that tended toward the settled area of Ar, and abuts the border of Moav” (Numbers 21:14–15). It was taught: “Et vahev besufa”; there were two lepers, named Et and Hev, who were walking at the rear [sof] of the camp of Israel. As Israel passed, the Emorites came and prepared caves for themselves and hid in them. They said: When Israel passes here we will kill them. But they did not know that the Ark of the Covenant preceded the children of Israel and would flatten mountains before them. When the Ark came, the mountains adhered one to another and killed the Emorites and their blood flowed down to the streams of Arnon. When Et and Hev arrived, they saw the blood that was emerging from between the mountains and they came and told Israel, who recited a song of praise. (Berakhot 54a)