Isaiah or Yeshayáhu (יְשַׁעְיָהוּ "Salvation of/is the LORD", Standard Hebrew Yəšaʿyáhu, Tiberian Hebrew Yəšaʿăyāhű) was the son of Amoz, and commonly considered the author of the Book of Isaiah. He was apparently of humble rank (Isa. 1:1; 2:1).
Isaiah was married to a woman called "the prophetess" (8:3), either because she was endowed with the prophetic gift, like Deborah (Judges 4:4) and Huldah (2 Kings 22:14-20), or simply because she was the wife of "the prophet" (Isa. 38:1). He had two sons, who bore symbolic names.
He exercised the functions of his office during the reigns of Uzziah (or Azariah), Jotham, Ahaz, and Hezekiah (1:1), the kings of Judah. Uzziah reigned fifty-two years in the middle of the 8th century BC, and Isaiah must have begun his career a few years before Uzziah's death, probably in the 740s BC. He lived till the fourteenth year of Hezekiah, and in all likelihood outlived that monarch (who died 698 BC), 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" (Isa. 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 Tiglath-Pileser III (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 Israel (2 Kings 16:5; 2 Chronicles 28:5, 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 V determined wholly to subdue the kingdom of Israel. Samaria was taken and destroyed (722 BC). So long as Ahaz reigned, the kingdom of Judah was unmolested by the Assyrian power; but on his accession to the throne, Hezekiah, who was encouraged by Isaiah to rebel "against the king of Assyria" (2 Kings 18:7), entered into an alliance with the king of Egypt (Isa. 30:2-4). This led the king of Assyria to threaten the king of Judah, and at length to invade the land. Sennacherib (701 BC) led a powerful army into Judah. 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 led an army into Judah, one detachment of which threatened Jerusalem (Isa. 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). According to the account in Kings (and its derivative account in Chronicles) the judgement of God now fell on the Assyrian army. "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 Chr. 32:23, 27-29). Isaiah probably lived to its close, and possibly into the reign of Manasseh, but the time and manner of his death are not specified in either the Bible or recorded history. There is a tradition that he suffered martyrdom in the pagan reaction in the time of Manasseh. Both Jewish and Christian traditions state that he was killed by being sawed in half. Some interpreters believe that this is what is referred to by Hebrews 11:37 (in the New Testament), which states that some prophets were "sawn in two". It is also mentioned in the book of The Martyrdom of Isaiah that he lived into the days of Manasseh, and was also sawn in half with a wooden saw.