I am asking for help in trying to make you and others understand what is being talked about in Isaiah 40:21 - twinc
Isaiah is thought of as the greatest of the writing prophets.
His name means: The Lord Saves.
He was a contemporary of Amos, Hosea and Micah.
He began his ministry in 740 BC (the year King Uzziah died).
He was married and had two sons.
He died in 680 BC (under the reign of Manasseh)
He most likely spent all his life in Jerusalem (Judah).
His greatest influence was under King Hezekiah.
Isaiah lived during the period of Assyrian expansion and the decline of Israel.
In about 733, the King of Israel tried to pressure the King of Judah into joining into a coalition against Assyria.
The King of Judah (Ahaz) chose instead to seek help from the King of Assyria (Tiglath-Pileser). This decision was condemned by Isaiah.
Assyria did assist Judah and conquered the Northern Kingdom, Israel in 720 BC.
But in 701 BC the new King of Assyria, King Sennacherib, threatened Jerusalem itself.
King Hezekiah prayed earnestly to God and Isaiah predicted that God would force the Assyrians to withdraw from the city of Jerusalem. Isaiah warned Judah that her sin would bring captivity at the hands of the Babylonians. This took place in 586 BC, after Isaiah was already dead.
Isaiah is a book that unveils the full dimension of God's acts of judgement and salvation on behalf of His people, Israel.
Chapters 40 and 48:13 tell of Israel's Mighty Creator - God.
It speaks of the deliverance and restoration of Israel, the coming of the victorious God and unwavering strength for the weary exiles.
(taken from Zondervan NIV Study Bible 2008)