God had promised King David son of the shepherd Jesse of the tribe of Judah that his throne would last forever. But the sins of Solomon son of David caused Israel to be split (a schism) with ten tribes to the north continuing as Israel with their own kings and queen mothers and Judah in the south made up of Judah and Benjamin with some Levites for the priesthood.
Isaiah began his prophesying in the Reign of King Uzziah of Judah. He continued through the reign of Jotham and then came Ahaz who was just dreadful as kings went but he was to have a son.
Isaiah went to King Ahaz and said “Ask for a sign.”
Ahaz in a pretence at suddenly being holy said he couldn’t possibly ask God for a sign. He may very well have been too scared to hear what that sign would be. Isaiah said “Well God says you are getting a sign anyway.” I am sure his tone was a little snarky. “Behold,” said Isaiah as the Spirit filled him with what to say, “A maiden shall conceive and bear a son and he shall be called Emmanuel, God with us.”
Ahaz’ wife gives birth to Hezekiah meaning something like “take courage”. She saved this son from the fires of Molech the god who had consumed her other child at the behest of Ahaz. Sacrificing babies for wealth and power is an age old vileness and Molech has turned up in many forms but always with the same results; lots of dead babies.
In many ways Ahaz could be considered a type of Antichrist. He sets up a pagan altar in the Temple, desecrating it with sacrifices to another god. Surely this was an abomination.
When Hezekiah becomes king he tries to put things right. Through a renewal of the Passover he tried to bring all Israel together at least spiritually. But when Hezekiah died his son Manasseh went back to the bad old ways of worshipping like the pagans and child sacrifice.
Jesus uses the word Gehenna, the place of fire where Ahaz and Manasseh had made their children pass through fire – that is sacrificed their children for wealth and power; as a word for hell. Gehenna the place of fire is hell because the Molech gods were demons. (Ps 151 the prayer of Manasseh gives some hope that he repented in the end).
Isaiah’s prophecy was to be more fully fulfilled when a virgin conceived and bore a son, a branch from the root of Jesse. Jesus is God With Us and He is of the family of David, the tribe of Judah and through him all Israel is saved.