Verse 21: And they (Ex. 14:13, 14; 2 Chron. 20:17) stood every man in his place round about the camp: (2 Kings 7:7) and all the host ran, and cried, and fled.
[Standing in his place] They did this, therefore, so that the Midianites might believe these to be torch-bearers merely for the purpose of kindling a torch for other fighting men, and for extending light to discover enemies. Hence the Midianites were charging into mutual slaughter, thinking themselves to be invaded and attacked by their Israelite enemies, since they were not able to distinguish enemies from their own men (Bonfrerius, similarly Tirinus, Serarius, Montanus’ Commentary, Lapide). By standing they were feigning themselves to give passage to their largest forces, as if each trumpeter had led his own cohort of armed men (Lapide).
Every man in his place; as if they had only been torch-bearers to the several companies.
[And the camp was cast into confusion, וַיָּרָץ] [They vary.] It was broken up (Pagnine, Montanus), as if from רָצַץ, to crush or shatter (Vatablus). Others: they ran, or, they dashed about (Septuagint, Syriac, Munster, Tigurinus, Junius and Tremellius, Osiander, English, Dutch, Vatablus), as if from רוּץ, to run; that is, they began to be afraid and to rush hither and thither (Vatablus).
Verse 22: And the three hundred (Josh. 6:4, 16, 20; see 2 Cor. 4:7) blew the trumpets, and (Ps. 83:9; Is. 9:4) the LORD set (1 Sam. 14:20; 2 Chron. 20:23) every man’s sword against his fellow, even throughout all the host: and the host fled to Beth-shittah in Zererath (or, toward Zererath), and to the border (Heb. lip) of Abel-meholah, unto Tabbath.
[They were cutting one another down with mutual slaughter] Suspecting betrayal in their midst (Grotius). In the darkness and in such an alarming event they were holding all for enemies (Bonfrerius). God sent among them terror and blindness, so that they, thinking the Hebrews to be giving out slaughter in the midst of the camp, because of panic, because of the disorienting effect of sleep, because of grief and rage, were striking with the sword, each his neighbor and him pursuing, because the Israelites were pursuing them with continual sounding of the trumpets and with the brightness of their torches (Lapide). God sent among them such perturbation, that they did not recognize one another. Without doubt, the mind or heart of man is under the power of God. Sometimes He moves the mind of man in such a way that they might not see those things that are present, as in Genesis 19 and 2 Kings 6. Sometimes He moves them to sudden forgetfulness of things preceding, and introduces new ways and habits in the soul, just as in Genesis 11. Sometimes He moves to imprudence, so that they might not be able to judge of the most obvious things, as in 2 Samuel 17. Finally, Josephus says that here there are many nations with different languages, and on account of this they were thinking those of their own party to be enemies; which has an appearance of truth. But my judgment is inclined to the former reasons (Tostatus).
The LORD set every man’s sword against his fellow: They slew one another, either because they suspected treachery, and so fell upon those they first met with; which they might more easily do, because they consisted of several nations, as may be gathered from Judges 6:3, and Josephus affirms; or because the darkness of the night made them unable to distinguish friends from foes; or because the suddenness of the thing struck them with horror and amazement; or because God infatuated them, as he hath done many others. Compare 1 Samuel 14:20; 2 Chronicles 20:23.
[Beth-shittah, etc.] Where and what these places might be, it is not easy to define, when they do not occur elsewhere in the Sacred Scripture, except Abel-meholah, which was in the tribe of Manasseh on the near side of Jordan, as it is evident from 1 Kings 4:12. But the matter requires that the other places be in the same tract (Bonfrerius).
[Through Zererath] That is, the Field of Zartanah, as it is gathered out of 1 Kings 4:12. See Joshua 3:16 (Junius). And certainly the placement marvelously corresponds (Malvenda).
[And the border of Abel-meholah] Hebrew: unto the lip, coast, bank, etc., of Abel-meholah (Malvenda), that is, unto the bank of Jordan over against Abel-meholah. It is the place from which Elisha was to have arisen, 1 Kings 19:16 (Junius, Bonfrerius).
Abel-meholah; of which see 1 Kings 4:12; 19:16.
 Hebrew: וַיַּֽעַמְדוּ֙ אִ֣ישׁ תַּחְתָּ֔יו סָבִ֖יב לַֽמַּחֲנֶ֑ה וַיָּ֧רָץ כָּל־הַֽמַּחֲנֶ֛ה וַיָּרִ֖יעוּ וַיָּנִֽיסוּ׃
 Hebrew: וַֽיִּתְקְעוּ֮ שְׁלֹשׁ־מֵא֣וֹת הַשּׁוֹפָרוֹת֒ וַיָּ֣שֶׂם יְהוָ֗ה אֵ֣ת חֶ֥רֶב אִ֛ישׁ בְּרֵעֵ֖הוּ וּבְכָל־הַֽמַּחֲנֶ֑ה וַיָּ֙נָס הַֽמַּחֲנֶ֜ה עַד־בֵּ֤ית הַשִּׁטָּה֙ צְֽרֵרָ֔תָה עַ֛ד שְׂפַת־אָבֵ֥ל מְחוֹלָ֖ה עַל־טַבָּֽת׃
 Hebrew: צְרֵרָתָה.
 Hebrew: שְׂפַת.
 Antiquities 5:6.