1911 Encyclopedia Britannica
(Heb. Adoniyyah or Adoniyyahu, " Yah is Lord"), a name borne by several persons in the Old Testament, the most noteworthy of whom was the fourth son of David. He was born to Haggith at Hebron (2 Sam. iii. 4; 1 Ch. iii. 2). The natural heir to the throne, on the death of Absalom, he sought with the help of Joab and Abiathar to seize his birthright, and made arrangements for his coronation (1 Kings i. 5 ff.). Hearing, however, that Solomon, with the help of Nathan the prophet and Bathsheba, and apparently with the consent of David, had ascended the throne, he fled for safety to the horns of the altar. Solomon spared him on this occasion (1 Kings i. 50 ff.), but later commanded Benaiah to slay him (ii. 13 ff.), because with the approval of Bathsheba he wished to marry Abishag, formerly David's concubine, and thus seemed to have designs on the throne.
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Chisholm, Hugh, General Editor. Entry for 'Adonijah'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/a/adonijah.html. 1910.