Banded together (poiēsantes sustrophēn). See note on Act 19:40 (riot), but here conspiracy, secret combination, binding together like twisted cords.
Bound themselves under a curse (anethematisan heautous). First aorist active indicative of anathematizō, a late word, said by Cremer and Thayer to be wholly Biblical or ecclesiastical. But Deissmann (Light from the Ancient East, p. 95) quotes several examples of the verb in an Attic cursing tablet from Megara of the first or second century a.d. This proof shows that the word, as well as anathema (substantive) from which the verb is derived, was employed by pagans as well as by Jews. Deissmann suggests that Greek Jews like the seven sons of Sceva may have been the first to coin it. It occurs in the lxx as well as Mar 14:71 (which see and Luk 21:5); Act 23:12, Act 23:14, Act 23:21. They placed themselves under an anathema or curse, devoted themselves to God (cf. Lev 27:28.; 1Co 16:22).
Drink (pein̂piein). Second aorist active infinitive of pinō. For this shortened form see Robertson, Grammar, p. 343.
Till they had killed (heōs hou apokteinōsin). First aorist active subjunctive of apokteinō, common verb. No reason to translate “had killed,” simply “till they should kill,” the aorist merely punctiliar action, the subjunctive retained instead of the optative for vividness as usual in the Koinéš (Robertson, Grammar, pp. 974-6). Same construction in Act 23:14. King Saul took an “anathema” that imperilled Jonathan (1Sa 14:24). Perhaps the forty felt that the rabbis could find some way to absolve the curse if they failed. See this verse repeated in Act 23:21.