2 Kings - Chapter 16

In 2 Samuel 7 God had made a promise to David:

“When your days are fulfilled and you rest with your fathers, I will set up your seed after you, who will come from your body, and I will establish his kingdom. He shall build a house for My name, and I will establish the throne of his kingdom forever. I will be his Father, and he shall be My son."

This promise was ultimately fulfilled in Jesus.  At the start of his ministry God spoke of the father/son relationship:

"When He had been baptized, Jesus came up immediately from the water; and behold, the heavens were opened to Him, and He saw the Spirit of God descending like a dove and alighting upon Him. And suddenly a voice came from heaven, saying, “This is My beloved Son, in whom I am well pleased.”"

King Ahaz, as a descendent of David, could claim the fatherhood of God; but instead he went to the King of Assyria, and gave him the role of father:

"So Ahaz sent messengers to Tiglath-Pileser king of Assyria, saying, “I am your servant and your son."