Judges 12 is a short chapter with few comments from the SAB. It's funny, but I was reading this on my own over the weekend, and I anticipated what the comments would be; that's not always easy to do, as the SAB can be full of surprises.
Anyway, as yet another sad footnote on the time of Jephthah's rule, we see a bizarre and bloody fallout of this war that shows itself in some sort of intertribal warfare. I think this is the first time we see such a thing in Israel, but unfortunately it won't be the last. Men from Ephraim come to Jephthah and complain that they didn't get to take part in the battle. (Most likely, they wanted a share of the spoils of war.) Jephthah points out to them that the trouble had been going on a long time before the fighting broke out, and they had been asked for help before, a request that was ignored. Fighting breaks out, and a lot of slaughter ensues. In the midst of this, the infamous "shibboleth" event happens. Apparently, in those days it wasn't so easy to tell who was an ally or enemy. In this case, however, a known difference between these two tribes was that the Ephraimites apparently don't use the "sh" sound in their speech. So when a soldier came to the river to cross, he might pretend to be whoever he wanted to be, but the soldiers on Jephthah's side would ask the person trying to cross to say the Hebrew word for "stream". Ephraimites would give themselves away by pronouncing it "sibboleth". The guards would know they were an enemy and pluck them out of the water and kill them. Violent? Most definitely. Unjust? Well, the Ephraimites were waging a completely unprovoked war against the men of Gilead, so what can you say?
By the way, I expected it might be said that 42,000 were killed in this manner, but I also realized upon reading the passage that such a guess was probably a misunderstanding of the text, for what it's worth. I think the intended meaning is that 42,000 Ephraimites were killed in total on the whole battlefield; the thought of killing them one by one as they crossed the river seems unlikely, and the text does not expressly say that.
The chapter closes with short and quick notes on three judges that follow Jephthah. Abdon in particular is apparently funny to Steve Wells for another mention of donkeys. It might be worth noting that while the KJV says "forty sons and thirty nephews", I'm not sure where that translation comes from. The Hebrew says literally "sons' sons", which surely ought to be "grandsons" as other translations render it.
And next time, we come to Samson, one of the oddest characters the Bible has to offer.