“Comfort, comfort my people” says your God. That’s the beginning of the OT lesson. Isaiah 40 speaks to a time around 587 BC.
However, there is a gap of 125 years between chapter 40 and chapter 39. In about 711 BC envoys came from Babylon to King Hezekiah of Judah. He is so honored, that he shows them his “Fort Knox” and his military command center and weapons.
The prophet Isaiah asks what he has shown these visitors. “Everything.” Hezekiah wants to form an alliance to counter Assyria, who had captured the ten northern tribes of Israel.
But Isaiah tells him Yahweh’s word. Babylon will come and carry away everything and Hezekiah’s descendants will serve the king of Babylon.
In that space between chaps 39-40, was the terrible 55- year reign of Manasseh (2 Kings 21). The 2-year reign of Amon. Then Josiah ruled. He tried to undo the harm of Manasseh. During a repair of the temple they found the Book of Deuteronomy and discovered they had been neglecting to celebrate Passover. However, Josiah was killed in 605 in a battle against Egypt at Megiddo. Babylon rose to power. Nebuchadnezzar attacked Jerusalem and destroyed the city and the temple in 587.
Jerusalem was in ruins. The temple destroyed. Into that dark time God calls, “Comfort, comfort, my people.”
When the times are the darkest, that is where the gospel seeks to shine its brightest, with hope.