ABIATHAR (Heb. אֶבְיָתָר; "the divine father excels"), son of *Ahimelech son of Ahitub of the priestly house of Eli of Shiloh (i Sam. 22:20 ff.). Abiathar was one of David's two chief priests. When the priests of the village of Nob were massacred by order of Saul because they had aided David, Abiathar alone escaped. He then reported the massacre to David, who asked him to join him as his priest. He brought with him an ephod, which was used by the priests as an oracle. David twice asked Abiathar to use the ephod to ascertain God's command (i Sam. 23:6, 9 ff.; 30:7 ff.). When David became king, Abiathar's line was established as the priestly line of the royal court along with *Zadok's (ii Sam. 8:17). It has been suggested, therefore, that the listing of Ahimelech (Abimelech) son of Abiathar as David's priest (ii Sam. 8:17; i Chron. 18:16) should be emended to read Abiathar son of Ahimelech, as in the Syriac version. During *Absalom's revolt David was forced to leave Jerusalem, but he sent Abiathar and Zadok there to inform him of the happenings in Absalom's court (ii Sam. 15:25, 34 ff.). There they had freedom of movement and thus were able to deliver messages to David about the rebel's intrigues (ii Sam. 17:15). Abiathar carried David's message of reconciliation to Amasa and the elders of Judah (ii Sam. 19:12) and also served as David's counselor (ii Sam. 15:27, 29; 17:15 ff.; 19:12 ff.; i Chron. 27:33–34). During the struggle for succession to David's throne, Abiathar supported *Adonijah (i Kings 1:7); hence Solomon, who was anointed by Zadok, banished Abiathar and his descendants to Anathoth and took away his privileges to act as priest in Jerusalem (i Kings 1:19, 25; 2:22, 26, 35). The prophet Jeremiah was descended from the priests of Anathoth and Jeremiah may have been a descendant of Abiathar (Jer. 1:1).
In the Aggadah
Abiathar was indirectly responsible for the continuation of the line of David. Had Abiathar not been saved from the massacre of the priests of Nob, there would have been no *Jehoiada to save the sole survivor of the Davidic line from the massacre instigated by *Athaliah (Sanh. 95b). Abiathar's replacement by Zadok as high priest is explained by the fact that the Urim and Thummim would not answer him when he consulted them (Sot. 48b). The Zohar (i 63b) illustrates his straitened circumstances thereafter (cf. i Kings 2:26) by the comment: "He who during David's lifetime lived in affluence and wealth, was reduced by Solomon to poverty."
M. Cogan, i Kings [ab] (2000), 177–78.
"Abiathar." Encyclopaedia Judaica. . Encyclopedia.com. (September 18, 2018). http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/abiathar
"Abiathar." Encyclopaedia Judaica. . Retrieved September 18, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/abiathar