Esaias is the Greek rendering of the Hebrew name, Isaiah, an Old Testament prophet. 

In the Hebrew Bible, the book of Isaiah is considered one of the major prophetic books, so named because of the size of the books. The books of the major prophets are made up of Isaiah, Jeremiah, and Ezekiel. This is not to say the major prophets are any more important, but only that the books are larger than books written by other prophets, called the minor prophets. 

Isaiah was the son of Amoz. His name means “The Lord saves.” He was a contemporary of Amos, Hosea and Micah. Isaiah began his ministry in 740 B.C., in the year King Uzziah died. We are told this in Chapter 6, verse 1. According to Jewish tradition, he was sawed in half during the reign of Manasseh. This event is referred to in Heb 11:37. 

Isaiah was married and had at least two sons, Shear-Jashub (7:3) and Maher-Shalal-Hash-Baz (8:3). He spent most of his life in Jerusalem during the rule of King Hezekiah (see 37:1-2). Isaiah wrote during a period of upheaval that came with the expansion of the Assyrian empire and the decline of Israel.  

This was the time of the divided kingdoms of Judah in the south and Israel in the north. In 745-727 B.C. the Assyrians march west into Aram (Syria) and Canaan. In 733 the kings of Aram and Israel went to Ahaz king of Judah and demanded he form a coalition against Assyria. Ahaz, king of Judah saw an opportunity to betray and attack Israel. Ahaz asked Tiglath-Pileser for help in battle.  

Judah formed an alliance with Assyria and conquered the northern kingdom in 722-721. The alliance made Judah vulnerable. King Hezekiah had taken the throne of Judah. In 701 BC King Sennacherib of Assyria threatened Jerusalem. King Hezekiah of Judah prayed earnestly, and Isaiah predicted that God would force the Assyrians to withdraw from the city, but Isaiah went on to foretell the fall of Judah and captivity at the hands of Babylon. Isaiah saw that God would redeem his people from Babylon and in one of his greatest and most powerful prophecies, Isaiah predicted the rise of Cyrus, who would rise to be king of the Persian unite the Medes and Persians. Cyrus would conquer Babylon in 539 and in 537 he would set the captives free.