The Lord is the one you must worship. The Lord brought you up out of Egypt by his great power. He saved you by reaching out his mighty arm. You must bow down only to him. You must offer sacrifices only to him.
All of this took place because the Israelites had sinned against the Lord their God. He had brought them up out of Egypt. He had brought them out from under the power of Pharaoh, the king of Egypt. But they worshiped other gods.
Then Isaiah the prophet called out to the Lord. And the Lord made the shadow go back ten steps. It went back the ten steps it had gone down on the stairway Ahaz had made.