(Heb. Yesh'yahu, i.e., "the salvation of Jehovah").
He exercised the functions of his office during the reigns of Uzziah (or Azariah), Jotham, Ahaz, and Hezekiah ( 1:1 ). Uzziah reigned fifty-two years (B.C. 810-759), and Isaiah must have begun his career a few years before Uzziah's death, probably B.C. 762. He lived till the fourteenth year of Hezekiah, and in all likelihood outlived that monarch (who died B.C. 698), and may have been contemporary for some years with Manasseh. Thus Isaiah may have prophesied for the long period of at least sixty-four years.
His first call to the prophetical office is not recorded. A second call came to him "in the year that King Uzziah died" ( Isaiah 6:1 ). He exercised his ministry in a spirit of uncompromising firmness and boldness in regard to all that bore on the interests of religion. He conceals nothing and keeps nothing back from fear of man. He was also noted for his spirituality and for his deep-toned reverence toward "the holy One of Israel."
In early youth Isaiah must have been moved by the invasion of Israel by the Assyrian monarch Pul (q.v.), 2 Kings 15:19 ; and again, twenty years later, when he had already entered on his office, by the invasion of Tiglath-pileser and his career of conquest. Ahaz, king of Judah, at this crisis refused to co-operate with the kings of Israel and Syria in opposition to the Assyrians, and was on that account attacked and defeated by Rezin of Damascus and Pekah of Samaria ( 2 Kings 16:5 ; 2 Chr. 2 Kings 28:5 2 Kings 28:6 ). Ahaz, thus humbled, sided with Assyria, and sought the aid of Tiglath-pileser against Israel and Syria. The consequence was that Rezin and Pekah were conquered and many of the people carried captive to Assyria ( 2 Kings 15:29 ; 16:9 ; 1 Chronicles 5:26 ). Soon after this Shalmaneser determined wholly to subdue the kingdom of Israel. Samaria was taken and destroyed (B.C. 722). So long as Ahaz reigned, the kingdom of Judah was unmolested by the Assyrian power; but on his accession to the throne, Hezekiah (B.C. 726), who "rebelled against the king of Assyria" ( 2 Kings 18:7 ), in which he was encouraged by Isaiah, who exhorted the people to place all their dependence on Jehovah ( Isaiah 10:24 ; 37:6 ), entered into an alliance with the king of Egypt ( Isaiah 30:2-4 ). This led the king of Assyria to threaten the king of Judah, and at length to invade the land. Sennacherib (B.C. 701) led a powerful army into Palestine. Hezekiah was reduced to despair, and submitted to the Assyrians ( 2 Kings 18:14-16 ). But after a brief interval war broke out again, and again Sennacherib (q.v.) led an army into Palestine, one detachment of which threatened Jerusalem ( Isaiah 36:2-22 ; 37:8 ). Isaiah on that occasion encouraged Hezekiah to resist the Assyrians ( 37:1-7 ), whereupon Sennacherib sent a threatening letter to Hezekiah, which he "spread before the Lord" ( 37:14 ). The judgement of God now fell on the Assyrian host. "Like Xerxes in Greece, Sennacherib never recovered from the shock of the disaster in Judah. He made no more expeditions against either Southern Palestine or Egypt." The remaining years of Hezekiah's reign were peaceful ( 2 Chronicles 32:23 2 Chronicles 32:27-29 ). Isaiah probably lived to its close, and possibly into the reign of Manasseh, but the time and manner of his death are unknown. There is a tradition that he suffered martyrdom in the heathen reaction in the time of Manasseh (q.v.).