{Banded together} (poi(8873)antes sustroph(886e)). See on  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
anathematiz(935c), 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  Mr 14:71  (which see and  Luke
21:5 );  Ac 23:12,14,21 . They placed themselves under an
anathema or curse, devoted themselves to God (cf.  Le 27:28f.  1Co 16:22 ). {Drink} (pein=piein). Second aorist active
infinitive of pin(935c). For this shortened form see Robertson,
_Grammar_, p. 343. {Till they had killed} (he(9373) hou
apoktein(9373)in). First aorist active subjunctive of apoktein(935c),
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 _Koin(825f) (Robertson, _Grammar_, pp. 974-6). Same
construction in verse  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 verse  21 .