מִשָּׁם֮ נָסָעוּ֒ וַֽיַּחֲנ֗וּ מֵעֵ֤בֶר אַרְנוֹן֙ אֲשֶׁ֣ר בַּמִּדְבָּ֔ר הַיֹּצֵ֖א מִגְּב֣וּל הָֽאֱמֹרִ֑י כִּ֤י אַרְנוֹן֙ גְּב֣וּל מוֹאָ֔ב בֵּ֥ין מוֹאָ֖ב וּבֵ֥ין הָאֱמֹרִֽי׃
E, partindo dali, acamparam-se além do Arnom, que está no deserto e sai dos termos dos amorreus; porque o Arnom é o termo de Moabe, entre Moabe e os amorreus.
Rashi on Numbers
מגבל האמרי The word גבול denotes boundary-line of (marking) the end of their frontier. Similar is the term the גבול of Moab (in this verse): it is an expression for extremity and end.
Ramban on Numbers
FOR ARNON IS THE BORDER OF MOAB, BETWEEN MOAB AND THE AMORITES. Arnon was a city which belonged to Moab, [located] near the end of the Amorite border and the beginning of the border of Moab, and it was situated on brooks that flowed through it.258Verse 14: and Arnon among the brooks.
Sforno on Numbers
מעבר ארנון...היוצא, in that region where the river Arnon borders the region where the desert starts.