Rabbi Chiya bar Aba said in the name of Rabbi Yochanan, “Why is it (the Jordan River) called Yarden? Because it flows down from Dan.”
We find in our sugya a lively discussion regarding the opinion of Rabbi Meir in the mishna that the Yarden serves as a halachic “divider” for the purpose of ma’aser beheima. Rabbi Meir states that if five animals are in a village on one side of the Yarden and five more animals are in a village on the other side, the Yarden prevents these animals in the nearby villages from combining to constitute the minimum number of animals necessary for the mitzvah.
Where, exactly, is the upper part of the Yarden? Rami bar bar Chama said in the name of Rabbi Yochanan that “above a place called Beit Yericho the river is not considered the Yarden” (because the part of the river above there is mixed with and considered part of the large bodies of water which form its source – Rashi).
However, Rabbi Chiya bar Aba said in the name of Rabbi Yochanan, “Why is it called Yarden? Because it flows down from Dan.” The river’s name is an acronym for yored, which means “goes down,” and Dan, which is the name of one of the tribes of Israel and the name of its portion of the Land in the north of the country. This seems to plainly indicate that the Yarden extends all the way to the northern border of Eretz Yisrael, unlike the opinion that it went up only until Beit Yericho. One might be tempted to reconcile these statements by stating that the place called “Dan” mentioned here is actually the name of a place near Beit Yericho, and not the portion of Eretz Yisrael allotted to the tribe of Dan in the north.
But we see from the Maharsha that this is not the case. The Maharsha asks: How could the river be called Yarden in the Chumash since “Dan” was not allotted his portion of Eretz Yisrael until later when the Land was conquered and divided. It is evident that the Maharsha understands the acronym “Yored m’Dan” to refer to the land of the tribe of Dan, which is certainly the normal understanding of the words. The Maharsha answers his question in the following way: The portion of Dan as part of the name of the Yarden is alluded to in the Chumash because it would be called that name in the future. He adds that we find a similar example in the Torah when it states that the Chidekel (Tigris) River “flows to the east of Assyria.” (Gen. 2:14) Although, he explains, there was no Assyria in existence at the time of the Garden of Eden, the verse refers to the name by which the place would be called in the future. The entire Chumash is prophetic.
- Bechorot 55a