The answer is: Touching dead bodies

Lev 21:1 - Priests had to maintain ceremonial cleanliness to perform their duties. An exception was made for close relatives.

Leviticus is like the ultimate rulebook for the ancient Israelites, and it gives some fascinating insight into the role of priests in their society. Priests were seen as the intermediaries between the people and the divine, so keeping a squeaky clean image wasn't just about aesthetics; it ensured the sanctity of the rituals they performed. Imagine being a priest and having to keep up with all those ritual cleanliness laws—now that’s a tough gig!

Touching corpses, something that most people wouldn't have thought twice about in their daily lives, was strictly off-limits for priests—except for family members. This reflects the strong communal values of the society, framing personal loss within strict cultural guidelines. In fact, even modern funeral practices remind us of this tension between duty and grief.

Interestingly, this emphasis on cleanliness echoes across cultures and religions, highlighting perhaps a universal human desire for purity when approaching the sacred. The priests had to wash and offer sacrifices before stepping into service, symbolizing their transformation before engaging with the spiritual realm.

Something else to ponder: While these rituals appear rigorous, they emphasize respect for the creator and the importance of holy spaces—dwellings governed by cleanliness, where the presence of the Divine could dwell. This principle invites us to reflect on the modern arenas in which we seek purity, both in physicality and morality.