In the days of Ahaz the son of Jotham, son of Uzziah, king of Judah, Rezin the king of Syria and Pekah the son of Remaliah the king of Israel came up to Jerusalem to wage war against it, but could not yet mount an attack against it. When the house of David was told, “Syria is in league with Ephraim,” the heart of Ahaz and the heart of his people shook as the trees of the forest shake before the wind.
And the Lord said to Isaiah, “Go out to meet Ahaz, you and Shear-jashub your son, at the end of the conduit of the upper pool on the highway to the Washer's Field. And say to him, ‘Be careful, be quiet, do not fear, and do not let your heart be faint because of these two smoldering stumps of firebrands, at the fierce anger of Rezin and Syria and the son of Remaliah. Because Syria, with Ephraim and the son of Remaliah, has devised evil against you, saying, “Let us go up against Judah and terrify it, and let us conquer it for ourselves, and set up the son of Tabeel as king in the midst of it,” thus says the Lord God:
“It shall not stand, and it shall not come to pass. For the head of Syria is Damascus, and the head of Damascus is Rezin. And within sixty-five years Ephraim will be shattered from being a people. And the head of Ephraim is Samaria, and the head of Samaria is the son of Remaliah. If you are not firm in faith, you will not be firm at all.”
Again the Lord spoke to Ahaz, “Ask a sign of the Lord your God; let it be deep as Sheol or high as heaven.” But Ahaz said, “I will not ask, and I will not put the Lord to the test.” (Is. 7:1-12)
Years have passed since Isaiah's recommision by the time of King Ahaz, the wicked king of Judah. After Uzziah was Jotham, and then Jotham's son King Ahaz, who was a wicked king, even burning his son as a sacrifice in the manner of the heathen (2 Ki. 16:3). King Rezin of Syria and King Pekah of Israel decided to combine forces and war war against Judah (v. 1), and the power of the combined armies of these two nations shook the confidence of evil King Ahaz and his people, who has been previously defeated by the Syrians already (2 Chron. 28:5) In fact, so shaken was Ahaz that he allied himself with the rising Assyrian empire to the north in order to defeat this strong coalition (2 Ki. 16:7-9), which will prove severely detreimental later on of course.
In the midst of the two-pronged attacks on Judah, God called Isaiah to encourage Judah and tell King Ahaz that their attack would fail. In fact, Isaiah was to go with his son to meet King Ahaz in person to deliver this enouraging message (v. 3). Judah was told to be careful, quiet and cautioned not to fear at the angers of Syria and Israel, whom God likened to 'two smouldering stumps of firebrands' (v. 4). God further revealed the enemies' plan against Judah; that they are planning to take over the kingdom and install a pupet ruler (the son of Tabeel — probably a non-Jew) to govern the area (v. 5-6). Yet God pronounces encouragement to Ahaz and proclaimed that their plan would not come to pass (v. 7). God mocked both Syria and Israel, saying that the head of Syria is Damascus and the head of Damascus is Rezin (v. 8a), thus basically belittling the threat of Syria and focusing it on the person of Rezin of which God has already providentially planned to remove from the equation (through Assyria cf 2 Ki. 16:9). As for Israel or Ephraim, God prophesied their destruction as a people (v. 8b), focusing their threat also to Samaria and then to the 'son of Remaliah' (v. 9a). Isaiah then told Ahaz to stand strong, telling him that if he cannot be firm in his faith, he will not be firm at all (v. 9b).
Now, this account has a lot of puzzling things which we shall need to clear up. For example, why is God helping the wicked king Ahaz here, after punishing him severely for his syncretism by giving him over to the Syrians earlier (2 Chron. 28:5)? In fact, as we look further down, King Ahaz acknowledges the LORD to be his God (v. 10-12), but doesn't the Scriptures say that he is wicked and even offered his son as a sacrifice 'according to the despicable practices of the nations whom the LORD drove out before the people of Israel' (2 Ki. 16:3)?
It must here be noticed that we have earlier shown that Judah was practicing syncretism. Therefore, Judah were being "innovative in worship" by incorporating the rites and rituals of pagan religion into the worship of the true God YHWH. It must be noted that Ahaz was not stated as worshipping other gods like Baal, Asheroth or Molech, but only that he followed their customs. We can therefore infer that even the sacrificing of his son was a vile custom adopted from the pagans in worhipping Yahweh. In his own mind, therefore, he most probably thought of himself a worhipper of the one true God, which he acknowledges even (cf v. 11-12). That of course does not mean that God accepted his wicked and compromising actions, but it shows forth God's kindness even to the wicked.
God, therefore, in protecting Judah was not so much an approval of Ahaz's deplorable compromise but rather of protecting the holy seed as the time has not yet come for the judgment and destruction of Israel. This is not to mention that the two nations coming against Israel were much worse, especially Apostate Israel which would be destroyed as a nation in the next generation of kings (King Hoshea son of Elah killed King Pekah son of Remaliah and was king when the Assyrians wiped Israel off the map — nationally and ethnically through deportation). God therefore protected Judah despite her continuing wickedness and the personal wickedness of King Ahaz. Also, since the plan of Syria and Ephraim was to install a pupet king who is probably a godless pagan on the throne (the name Tabeel seems to be a pagan name since it is also the name of a pagan living in the time of King Artexerses of Persia (Ezra 4:7)), that would have implications on the Covenental Sucession of the Davidic Kingship, that would be contrary to God's plan. God therefore intervenes to foil such a wicked plan, for the sake of His Covenant.
It must be remembered that the earlier kings especially King Uzziah had fortified the country even with powerful war machines resembling ballistas and catapults (2 Chron. 26:15), numerous towers and cisterns (2 Chron. 26:9-10) and a strong, well-armed and trained army (2 Chron. 26:11-14). All of these came in handy during the war with Rezin of Syria and Pekah of Israel/Ephraim. We must here note that God does not always have to help through supernatural aids; hail, lightening or by 'the angel of death', but also through the use of providence, which He most certainly uses in this case.
Yet even with this, the strong armies of Syria and Israel were almost too much to bear, that Ahaz with only physical eyes and strict military calculations loses heart and begin to despair (v. 2), especially after God has punished him earlier with defeat. Isaiah therefore was sent to call him to have faith in God, although he has compromised the faith already, yet God as the covenanting God still called him to stand firm, because God has already ordained that they will not succeed, although they may seem to be wnning. In point of fact, they were much weakened through attrition even as they battled through to Jerusalem, thus their comparison with 'smouldering stumps of firebrand' too. As we know, Ahaz in the end did not have faith in God, but asked the Assyrians for help (2 Ki. 16:7-9), though it is very likely given God's promise that even if the Assyrians have not helped Judah, Syria and Israel would have wore themselves out militarily before they could defeat Judah; what they have is probably just the last show of force.
It would do us good to look at the meaning of the name of Isaiah's son Shear-jashub, which means 'A remnant shall return'. Isaiah thus expresses his hope in God that God's promises of protection of a remnant of Israel, and that they will one day be restored by the grace of God. In it, we can learn similarly to put our trust in God and His promises even if the situation does not present itself as being that way, and take hold of God's promises by faith not by sight.
King Ahaz is therefore both a product and a perpetuator of the wickedness of the society in his time. The pervasive and continuous syncretism and compromise practiced by the nation of Judah had an impression on him and influenced him in his wickedness. And he in turn perpetuate such wickedness, causing the judgment of God to come upon the nation in sending the confederacy of Syria and Israel to attack the formerly strong nation of Judah, even giving Judah over to their hands for a time. From this, we should learn not to just allow sin in the church, as it will soon work its way to the leaders of the church. For when it comes to that stage, God will pour out His judgments on the church severely. Yet, God is merciful, although we should never presume on his mercy as if he must protect the church regardless of whatever she does (Jerusalem learnt that lesson bitterly when the Babylonians sacked her and burned her to the ground several generations later). In this case, God had mercy and saved Judah and King Ahaz, not because of Ahaz's sake, for Ahaz deserved nothing but death, but because of the sake of His Covenant with David. From this, we can learn that God because of His Covenant with us will not punish us so severely as to destroy us, but that He will still preserve us, a remnant chosen by grace, as symbolized by the name of Isaiah's son.
 As long as Judah was a nation and has a king, the person sitting on it must be of the Davidic line. Only when Judah was destroyed was the Covenental Sucession 'suspended' until its final fulfilment in Jesus Christ our Lord, the Son of David.