Final answer:
On Shavuot, the Book of Ruth is read, reflecting themes of loyalty, conversion, and harvest which resonate with the holiday's celebration of the giving of the Torah and the spring harvest.
Step-by-step explanation:
The megillah read on Shavuot is the Book of Ruth. The reading of Ruth during this holiday is rich in symbolic meaning. Shavuot celebrates the giving of the Torah on Mount Sinai and also marks the spring harvest. The story of Ruth is about loyalty, devotion, and the acceptance of Judaism, which resonates with the themes of receiving the Law. Furthermore, Ruth herself is a figure of conversion to Judaism, and her gleaning in the fields of Boaz symbolizes the harvest aspect of the holiday.