The answer lies in the realm of halakhah, the Jewish laws of ritual purity. The Mishnah tells us that stone vessels are among those objects that are not susceptible to uncleanness...
मिश्‍नाह हमें बताता है कि पत्थर के बर्तन उन वस्तुओं में से हैं जो अशुद्ध नहीं होते...