Rashi on Deuteronomy 3:16/רש"י על דברים ג׳:ט״ז

1תוך הנחל וגבול THE MIDST OF THE BROOK AND THE TERRITORY, i.e., all the brook and in addition, land on its opposite bank. The words therefore are as much as to say, עד "unto” the Brook of Arnon, ועד "and” that which is mentioned as being "unto” (i.e. the Brook itself) is included (by the words תוך הנחל), and even more than this (namely, the גבול, land on the other side of the brook).