1) Besides its basic meanings (bind, constrict, show hostility, vex), Hebrew ṣrr can also denote the act of ‘rivalling’ or being a rival. Thus ṣrr's derivative noun ṣrh (pl. ṣrt), like its Akkadian cognate ṣerretu, stands for ‘rival’ – particularly a rival-wife (see 1Sam 1:6; M. Yev. 1.1 and passim). Accordingly, liṣror comes into its own if the focus of Lev 18:18 is rival wives. But if the focus is sisters, liṣror would seem otiose. Nor does it help that it is absent from the ‘woman and her daughter’ prohibition (18:17).

2) Verse 18 ends with the qualifying phrase be-ḥayyehah (in her lifetime), implying that with the wife's death, the union ceases to be unlawful. This provision is extraordinary; nowhere does Torah teach that affinity to one's spouse's kin dissolves with the spouse's death. As noted, the Talmud sided with the ‘builders’, taking the subject of Lev 18:18 to be biological sisters. Hence, rabbinic texts allow marriage to a deceased wife's sister. This exceptional leniency stands out like a sore thumb, as Maimonides's code will illustrate: