In this verse, God instructs the priests to maintain a high level of holiness and purity in their lives, especially in times of mourning. They are prohibited from defiling themselves by participating in certain mourning rituals, such as shaving their heads or cutting their bodies. This command emphasizes the importance of the priests' consecration and separation from common practices, highlighting the need for them to set a holy example for the people. By adhering to these regulations, the priests demonstrate their commitment to honoring God and upholding His standards of holiness.