Took Ish Boshes. He extrapolated from a verse that two kings were destined to come from Binyomin. Because the Holy One, blessed is He told Yakov, "Kings will come forth from you," and [by this time] all of his children had been born except for Binyomin.¹

footnotes: ¹ “Will come forth from you” implies that they were to come from someone yet unborn, and this could only be Binyomin. Avner understood this to mean that two kings will be descendant from Binyomin, Shaul and Ish Boshes (Rashi and Sifsei Chachomin, Breshis 35,11).

The Plain of Swords. Yonasan translates the plain of Killing on account of the swords just like you say [in Scriptures] (Tehilim 89, 44)² "You also turned back the sharpness of his sword."

footnotes: ² Rashi is showing how the word צוּר, sharpness, is used in reference to a sword.

Into the fifth rib. As [if to say] the fifth rib,³ the place where the bile and the liver are set. [But] Yonasan translated [this to mean] "on the side of his thigh,"

footnotes: ³ Counting from the bottom.

And died in his place. And died in his place.⁴

footnotes: ⁴ This is Targum Yonasan’s translation.

If you had not spoken. If only you had spoken this [way⁵ earlier] [The לא] is as [if it were written] לו⁶, meaning it. Another [way] to interpret it is as it's plain meaning⁷: if you had not spoken i.e. that which you said "Let the young soldiers get up and playfight."⁸

footnotes: ⁵ Your decrying of us fighting each other. ⁶ According to this first interpretation, the construct לוּלֵא denotes לוֹלוּ, “if only if,” i.e., if only you had spoken these reconcilitory words earlier. ⁷ This interpretation of לולא is the usual “if not for.” ⁸ Those words triggered this deadly battle.

The Bisron. The name of a region.

Nineteen men and Asoel. But is not Asoel included in [the group called] "the servants of Dovid," so why is he [singled] out? [The reason is] he was worth all of them [together] and so too [a similar case], (Yehoshua 2,1), "Go see [and spy out] the land and Yericho"⁹ and so too [another similar case] "King Shlomo loved many foreign women and the daughter of Pharaoh."¹⁰ (Kings I, 11, 1 ).

footnotes: ⁹ Yericho was as strong as the entire land combined (see Rashi there). ¹⁰ Shlomo cherished Pharaoh’s daughter as much as he did the rest of them put together. (See Rashi ibid).