The Jews for certain of the Jews, A.V. and T.R. Banded together ( ποιήσαντες συστροφὴν). This word συστροφή is found in the New Testament only here and Acts 19:40, where it is rendered "concourse."
The sense of "a conspiracy," which it has here, is common in the LXX. (see Amos 7:10; 2 Kings 15:15, etc.). The verb συστρέφειν in the LXX. has the sense of "to conspire" (2 Samuel 15:31; 2 Kings 10:9; 2 Kings 15:30, συνέστρεψε σύστρεμμα).
Bound themselves under a curse ( ἀνεθεμάτισαν ἑαυτοὺς). The word ἀνάθεμα (Romans 9:3; 1 Corinthians 12:3; 1 Corinthians 16:22; Galatians 1:8, Galatians 1:9) corresponds to the Hebrew ־שׂתס, the devotion of anything to destruction; and hence "the thing itself so devoted."
And the verb ἀναθεματίζεν corresponds to the Hebrew ־שׂתס, to devote to destruction, without the possibility of redemption. Here they made themselves an ἀνάθεμα if they did not kill Paul before partaking of any food.
It seems, however, that there was a way of escape if they failed to keep the vow. Lightfoot, on this passage, quotes from the Talmud: "He that hath made a vow not to eat anything, woe to him if he eat, and woe to him if he do not eat.
If he eat he sinneth against his vow; if he do not eat he sinneth against his life. What must such a man do in this case? Let him go to the wise men, and they will loose his vow" ('Hebrews and Talmud.
Exercit. upon the Acts').