Verse 15: And Moses gave unto the tribe of the children of Reuben inheritance according to their families.
[Moses gave] [Thus most interpreters.] Others: he had given (Junius and Tremellius, Masius), understanding, a possession (Vatablus).
[According to their families, לְמִשְׁפְּחֹתָם] Unto their families, or lineages; that is to say, for all and every one of their families, namely, what things were sufficient for them: not that Moses was distributing their possessions to the individual clans, much less to the families individually; for this was the duty of the tribunes, rulers overs tens, etc. (Masius).
According to their families: Dividing the inheritance into as many parts as they had families; but this is only spoken of the greater families; for the lesser divisions or distributions to the several small families was done by inferior officers, according to the rules which Moses gave them.
Verse 16: And their coast was (Josh. 12:2) from Aroer, that is on the bank of the river Arnon, (Num. 21:28) and the city that is in the midst of the river, (Num. 21:30; Josh. 13:9) and all the plain by Medeba…
[And the border was] Understanding, of their allotted region, etc.; that is to say, The region allotted to them includes, etc. (Vatablus). By border understand not the limits of the region, but the whole tract of the region (Bonfrerius).
[From Aroer] That is, exclusively; see verse 25: and Aroer was in the Tribe of Gad, Numbers 32:34 (Bonfrerius).
[On the bank of the torrent Arnon, עַל־שְׂפַת־נַ֙חַל אַרְנ֜וֹן] The נַחַל signifies torrent, not valley; for שָׂפָה, a lip, does not belong to valleys, but to rivers, that is, a bank (Drusius). Now, the following וְהָעִיר they translate, and the city (Septuagint, Pagnine, and others); as if it were different from Aroer: but it is the same city, as Jerome rightly observes. It is able to be translated from the Hebrew, from Aroer and the city, etc., so that that AND might be exegetical (Bonfrerius).
The city that is in the midst of the river; of which see Deuteronomy 3:16; Joshua 12:2.
[That leads to Medeba, עַל־מֵידְבָא] Near Medeba (Pagnine). Above, that is, next to, or near, Medeba. Thus Livy, upon the Numicius river (Drusius). Which lies near to the city Medeba (Vatablus); all the way unto Medeba (Chaldean). It is confirmed from this, that עַל/upon is the same as עַד/unto: in Genesis 49:13, עַל־צִידֹן, unto Zidon; in Psalm 48:14, עַל־מוּת, unto death (Drusius).
Verse 17: Heshbon, and all her cities that are in the plain; Dibon, and Bamoth-baal, and Beth-baal-meon (or, the high places of Baal, and the house of Baal-meon: see Numbers 32:38)…
[And Heshbon] The Reubenites had this in common with the Gadites, whence below it is said to be given to the Levites by the Gadites, Joshua 21:39. See Numbers 21:25 (Malvenda). But, if it was common, it was not able to be given by the Gadites alone (Drusius).
[Their hamlets, עָרֶיהָ] Her cities, that is, subordinate to her (Vatablus).
[Dibon] It is assigned to the Reubenites, but it appears rather to have pertained to the Gadites: whence Dibon-Gad, Numbers 33:45 (Drusius). But the city was situated on the border, and is therefore ascribed at one time to the one Tribe, at another time to the other (Masius, Bonfrerius). The same is to be said of Heshbon and some other cities (Bonfrerius).
Heshbon: this city and Dibon and Ataroth were upon the borders of Reuben and Gad, and therefore sometimes are ascribed to Reuben, as here, and Numbers 32:37, sometimes to Gad, as Numbers 32:34; 1 Chronicles 6:80, 81, by whom Heshbon, is said to be given to the Levites, Joshua 21:39. Possibly it and the rest were jointly inhabited by both tribes, as Jerusalem was by Jews and Benjamites.
[Bamoth-baal] It is the same as in Numbers 21:28. Baale-Bamoth-Arnon, that is, the Gods of the High Places of Arnon. בָּמוֹת/bamoth signifies high places, in which the nations worshipped their gods (Masius).
Bamoth-baal; of which Numbers 21:28.
[Baal-meon] Hebrew: Beth-baal-maon; it signifies the habitation, that is, the temple, or shrine, of Saturn, or Jove, or another tutelary god. Ezekiel, with Beth/house omitted, calls is Baal-meon, Ezekiel 25:9. Thus also Jerome, who writes that even within his own memory there was a large country district among the Moabites. Jeremiah, with the other part omitted, calls it Beth-meon, Jeremiah 48:23 (Masius).
Beth-baal-meon; called Beth-meon, Jeremiah 48:23, and Baal-meon, Ezekiel 25:9, part of the name being cut off, as is usual with the Hebrews.
Verse 18: (Num. 21:23) And Jahazah, and Kedemoth, and Mephaath…
 Hebrew: וַיִּתֵּ֣ן מֹשֶׁ֔ה לְמַטֵּ֥ה בְנֵֽי־רְאוּבֵ֖ן לְמִשְׁפְּחֹתָֽם׃
 Hebrew: וַיְהִ֙י לָהֶ֜ם הַגְּב֗וּל מֵעֲרוֹעֵ֡ר אֲשֶׁר֩ עַל־שְׂפַת־נַ֙חַל אַרְנ֜וֹן וְהָעִ֙יר אֲשֶׁ֧ר בְּתוֹךְ־הַנַּ֛חַל וְכָל־הַמִּישֹׁ֖ר עַל־מֵידְבָֽא׃
 Thus, the and might be rendered even.
 History of Rome 1:2:6. The Numicius River was probably near Lavinium, a port city, roughly thirty miles south of Rome. It is said that Æneas was buried upon the banks of the Numicius.
 Hebrew: חֶשְׁבּ֥וֹן וְכָל־עָרֶ֖יהָ אֲשֶׁ֣ר בַּמִּישֹׁ֑ר דִּיבוֹן֙ וּבָמ֣וֹת בַּ֔עַל וּבֵ֖ית בַּ֥עַל מְעֽוֹן׃
 Numbers 21:28: “For there is a fire gone out of Heshbon, a flame from the city of Sihon: it hath consumed Ar of Moab, and the lords of the high places of Arnonבַּעֲלֵ֖י) בָּמ֥וֹת אַרְנֹֽן׃, Baale-Bamoth-Arnon).”
 Hebrew: וּבֵ֖ית בַּ֥עַל מְעֽוֹן׃.
 מָעוֹן signifies little habitation.
 Hebrew: וְיַ֥הְצָה וּקְדֵמֹ֖ת וּמֵפָֽעַת׃