וְלָרֻאוּבֵנִ֨י וְלַגָּדִ֜י נָתַ֤תִּי מִן־הַגִּלְעָד֙ וְעַד־נַ֣חַל אַרְנֹ֔ן תּ֥וֹךְ הַנַּ֖חַל וּגְבֻ֑ל וְעַד֙ יַבֹּ֣ק הַנַּ֔חַל גְּב֖וּל בְּנֵ֥י עַמּֽוֹן׃
און צו די ראובֿנים און צו די גָדים האָב איך געגעבן פֿון גִלעָד און ביזן טאָל אַרנוֹן, דעם מיטן טאָל און דעם ברעג, און ביזן טײַך יַבוֹק, דעם געמאַרק פֿון די קינדער פֿון עַמוֹן;
Rashi
תוך 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).
Ibn Ezra
brook, and boundary i.e., and its boundary. Compare, the Jordan, and [its] bank.
Siftei Chakhamim
Until its opposite bank etc. I.e., the inheritance of the Gaddites, which was on the eastern side of the Yardein, continues across the western edge of Wadi Arnon. For the verse, “and the border,” means: “This is the border [of their inheritance],” which continues until the wadi on the western side [of the Yardein]. And then it continues up until and includes Yabok. For, “even more,” also includes Yabok.