The 87th prohibition is that we are forbidden from separating the breastplate [of the kohen gadol] from the ephod.

The source of this prohibition is G‑d's statement1 (exalted be He), "Do not separate the breastplate from the ephod" — instead, leave it attached.

In the end of tractate Makkos,2 when listing those who are punished by lashes, our Sages also said, "But there is also one who separates the breastplate, as prohibited by the verse, 'Do not separate the breastplate'!" This proves that one who does separate [the breastplate from the ephod in a destructive manner3] is punished by lashes.