The 164th prohibition is that kohanim are forbidden from entering the Temple grounds when their garments are torn.

The source of this prohibition is G‑d's statement,1 "Your garments lo sifromu; otherwise you will die." The Sifra explains, "The phrase, 'Your garments lo sifromu,' means 'Do not tear your garments.' "

This commandment is also repeated regarding the kohen gadol in the verse,2 "He may not tear his garments."

You should be aware that the kohen gadol may not tear his clothing in mourning [as others do] even when not performing the Temple service. This is the reason for the repetition. The Sifra says,3 "If his relative dies, 'he may not grow his hair long and he may not tear his garments,' i.e., in the same way that others grow their hair and tear their clothing when one of their relatives dies. How [is the tearing done]? The kohen gadol tears from the bottom [of the garment] and a regular kohen from the top [as is regularly done]."

One who performs the Temple service with torn garments is punished by a [Divine] death sentence, since the same law applies to both long hair and torn garments. [Therefore,] if one enters the Temple grounds in this condition, he [merely] transgresses a prohibition [but is not punished by death].

Only the kohen gadol is forbidden from growing his hair long and tearing his garments at all times, even without entering the Temple grounds. In this law, this is the difference between him and a regular kohen.