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.

In the book of Leviticus, the rules for priests serve not just as a hygiene guide but as a framework for spiritual conduct and reverence. When we dig deeper into the rite of maintaining purity, one intriguing aspect is the significance of life and death in Jewish culture. Priests, as intermediaries between God and Israel, were required to exemplify holiness; touching a dead body could symbolize a loss of life, which is essentially the opposite of what a priest's role represents. This contrast highlights a commitment to the pro-life values present throughout the Scriptures.

An interesting piece of trivia is found when we consider the ancient view of slaughter. Practices like circumcision and sacrifices mirrored the idea of life and vitality. The priests weren't purely dedicated to what happens in a physical realm—it's all interwoven with themes of life, cleanliness, and relationship with the divine.

It's also noteworthy that the exception made for close relatives points to a larger communal ethic—family was cherished, encouraging care and compassion. This concept resonates through various stories in the Bible, such as Jesus’ own healing of the dead or sick, where social taboos were boldly upheld in favor of compassion.

Thus, when considering regulations like those in Lev 21:1, we stand not only within a realm of legalism but find principles that echo throughout time, asserting a narrative of care, sanctity of life, and the weight of responsibility that comes with priestly duty. It positively shapes the community’s understanding of holiness, serving as both a spiritual rite and social guide.