Verse 19: If ye then have dealt truly and sincerely with Jerubbaal and with his house this day, then (Is. 8:6; Phil. 3:3) rejoice ye in Abimelech, and let him also rejoice in you…
[Today] At this time. Day is taken in the place of time (Drusius).
[Rejoice ye] That is to say, Let it be well between you and him; may God put a good turn upon that (Bonfrerius). Let that inauguration be happy and auspicious for the King (Vatablus).
Verse 20: But if not, (Judg. 9:15, 56, 57) let fire come out from Abimelech, and devour the men of Shechem, and the house of Millo; and let fire come out from the men of Shechem, and from the house of Millo, and devour Abimelech.
[Let fire come out from, etc.] This is not a prophecy (Bonfrerius), but an execration and imprecation, and that effectual. The curses of the just (and of those that are oppressed by force) frequently have force and effect; of which sort is that of Joshua 6:26, compared with 1 Kings 16:34, and that of Elisha, 2 Kings 2:24 (Lapide, Bonfrerius).
But if not, let fire, etc.: This is not a prediction, but an imprecation or curse, as it is called, verse 57, which, being grounded upon just cause, and being the only way by which Jotham could perform the duty of the avenger of his brethren’s blood, which was incumbent upon him, had its effect, as others in like case had, as Joshua 6:26, compared with 1 Kings 16:34; 2 Kings 2:24.
[From the men of Shechem, and let it devour Abimelech] But, you will say, neither the Shechemites, nor the citizens of Millo, killed him, but a woman of the city of Thebez. Responses: 1. Thebez and Millo appear to have been colonies of the Shechemites, whence both followed their Shechemites whether in receiving, or in rejecting, Abimelech (Bonfrerius). Thebez was in the borders of Shechem (Lapide out of Jerome). And Adrichomius makes it distant by only one stadium (Bonfrerius). 2. The Shechemites were the occasion why Abimelech was killed by the woman (Lapide, Bonfrerius): for the rebellion, having been initiated by them, spread to others (Bonfrerius).
Verse 21: And Jotham ran away, and fled, and went to (2 Sam. 20:14) Beer, and dwelt there, for fear of Abimelech his brother.
[And he departed unto Beer] There is no mention made of this place elsewhere in Scripture. It was eight miles distant from Eleutheropolis, says Jerome. But where is this Eleutheropolis, from which (as a city illustrious in his own time) Jerome often takes the distances of cities? Responses: 1. It was in the tribe of Judah; for generally speaking there are the cities that Jerome describes from a comparison with it. 2. Eleutheropolis is not Hebron; for Jerome thus writes elsewhere, Ceila toward the East of Eleutheropolis on the way to Hebron. 3. It was not far from Ælia, or Jerusalem. Therefore, Beer does entirely appear to have been in the tribe of Judah (Bonfrerius). בְּאֵרָה, that is, לַבְּאֵר, unto Beer. That expresses a well, or cistern (Drusius). Perhaps this is the place that in Joshua 19:8 is called Baalath-Beer in the tribe of Simeon (Junius).
Jotham ran away, and fled: He might easily flee, having the advantage of the hill and other accommodations for flight, and because the people were not forward to pursue a man whom they knew to have such just cause and great provocation to speak, and so little power to do them any hurt. Beer; a place remote from Shechem, and out of Abimelech’s reach. There were divers places of that name.
 Hebrew: וְאִם־בֶּאֱמֶ֙ת וּבְתָמִ֧ים עֲשִׂיתֶ֛ם עִם־יְרֻבַּ֥עַל וְעִם־בֵּית֖וֹ הַיּ֣וֹם הַזֶּ֑ה שִׂמְחוּ֙ בַּאֲבִימֶ֔לֶךְ וְיִשְׂמַ֥ח גַּם־ה֖וּא בָּכֶֽם׃
 Hebrew: וְאִם־אַ֕יִן תֵּ֤צֵא אֵשׁ֙ מֵאֲבִימֶ֔לֶךְ וְתֹאכַ֛ל אֶת־בַּעֲלֵ֥י שְׁכֶ֖ם וְאֶת־בֵּ֣ית מִלּ֑וֹא וְתֵצֵ֙א אֵ֜שׁ מִבַּעֲלֵ֤י שְׁכֶם֙ וּמִבֵּ֣ית מִלּ֔וֹא וְתֹאכַ֖ל אֶת־אֲבִימֶֽלֶךְ׃
 A stadium is about six hundred and twenty-five feet.
 Hebrew: וַיָּ֣נָס יוֹתָ֔ם וַיִּבְרַ֖ח וַיֵּ֣לֶךְ בְּאֵ֑רָה וַיֵּ֣שֶׁב שָׁ֔ם מִפְּנֵ֖י אֲבִימֶ֥לֶךְ אָחִֽיו׃
 Eleutheropolis was roughly thirty-three miles southwest of Jerusalem, on the way to Gaza.