Firm; a prince, a king of Syria, who joined Pekah (q.v.) in an invasion of the kingdom of Judah (2 Kings 15:37; 16:5-9; Isa. 7:1-8). Ahaz induced Tiglath-pileser III. to attack Damascus, and this caused Rezin to withdraw for the purpose of defending his own kingdom. Damascus was taken, and Rezin was slain in battle by the Assyrian king, and his people carried into captivity, B.C. 732 (2 Kings 16:9).