Final answer:
King Josiah of Judah was the leader who centralized worship in Jerusalem and is associated with the discovery of the Book of the Law during his religious reforms in the 7th century BCE.
Step-by-step explanation:
The good king of Judah who performed the centralization of worship in Jerusalem and discovered the Book of the Law was King Josiah. Reforms during his reign were significant as he imposed strict monotheism and oversaw the compilation of the first books of the Hebrew Bible, the Torah, in 621 BCE. This included the claim of discovering the Book of Deuteronomy, although historians generally agree that it was likely written at that time. King Josiah's reforms emphasized a move away from polytheistic traditions towards exclusive worship at the Temple of Jerusalem and adherence to Yahweh according to Mosaic laws.