Verse 17:[1] Then the children of Ammon were gathered together (Heb. cried together[2]), and encamped in Gilead. And the children of Israel assembled themselves together, and encamped in (Judg. 11:11, 29; Gen. 31:49) Mizpeh.
[Shouting together] That is, calling together their men for war (Lapide).
[In Gilead] Understand, either, 1. in the half tribe of Manasseh (Lapide, Bonfrerius), which in the strict acceptation of Gilead is called (Bonfrerius): or, 2. in the tribe of the Gadites: which I would prefer, because the Ammonites were pretending that that entire tract from Aroer to Jabbok was taken from them,[3] Judges 11:13, which was occupied by the Reubenites and the Gadites; but not that tract of land which was on the other side of the torrent Jabbok, and was possessed by the Manassites (Bonfrerius).
[In Mizpeh] It signifies a looking-glass,[4] and so there are multiple places called Mizpeh: 1. in Judah, Joshua 15:38; 2. in Benjamin, Joshua 18:26; Judges 20:1; 3. in Moab, 1 Samuel 22:3; 4. in Naphtali, Joshua 11:3; 5. and this one (Serarius). There was a twofold Mizpeh on the other side of Jordan, as we said on Joshua 11:3, one in Gad, the other in Manasseh. This one appears to have been the latter (Bonfrerius, Lapide); both because Jephthah dwelt there, who was a Manassite, see Judges 11:1 (Bonfrerius); and because the Ammonites had invaded the tribe of Manasseh neighboring to them (Lapide).
That Mizpeh which was beyond Jordan in Gad or Manasseh; of which see Genesis 31:49; Joshua 18:26; Judges 10:17; 11:11, 29, 34. There were other cities of that name in Scripture.
Verse 18:[5] And the people and princes of Gilead said one to another, What man is he that will begin to fight against the children of Ammon? he shall (Judg. 11:8, 11) be head over all the inhabitants of Gilead.
[He shall be the leader of the people of Gilead] Not only the general of the war, but the prince of the people of Gilead (Bonfrerius). With this reward they entice, etc., as Caleb did formerly[6] (Martyr). And thus at that time they did indeed determine by emergency counsel, but counsel not quite correct; whence afterwards they more correctly sent for Jephthah (Lapide out of Tostatus, similarly Serarius). This they determined, perhaps in council they were not agreeing concerning choosing a Commander-in-Chief, neither was anyone daring to undertake it. But what if whoever had undertaken arms first was a wicked man? Responses: 1. They hold all civil promises in this way, if they are able to be discharged by honest men. 2. Therefore, I think that this was a sign bestowed by God, and so they were certain that an evil Prince was not be given to them. Perhaps they had asked of the Lord a Leader, and had received a response, that they were to understand by this sign who was to be received as Leader; namely, he that had first begun to fight against the enemy. Sometimes God made use of such signs without a voice or external oracle, as in Genesis 24 (Martyr).
[1] Hebrew: וַיִּצָּֽעֲקוּ֙ בְּנֵ֣י עַמּ֔וֹן וַֽיַּחֲנ֖וּ בַּגִּלְעָ֑ד וַיֵּאָֽסְפוּ֙ בְּנֵ֣י יִשְׂרָאֵ֔ל וַֽיַּחֲנ֖וּ בַּמִּצְפָּֽה׃
[2] Hebrew: וַיִּצָּעֲקוּ.
[3] See Joshua 12:2.
[4] מִצְפָּה/Mizpeh is related to the verbal root צָפָה, to look out.
[5] Hebrew: וַיֹּאמְר֙וּ הָעָ֜ם שָׂרֵ֤י גִלְעָד֙ אִ֣ישׁ אֶל־רֵעֵ֔הוּ מִ֣י הָאִ֔ישׁ אֲשֶׁ֣ר יָחֵ֔ל לְהִלָּחֵ֖ם בִּבְנֵ֣י עַמּ֑וֹן יִֽהְיֶ֣ה לְרֹ֔אשׁ לְכֹ֖ל יֹשְׁבֵ֥י גִלְעָֽד׃
[6] Joshua 15:16; Judges 1:12.