The prophet delivers a harsh rebuke regarding a severe violation of the Temple's sanctity. A sacred space requires fierce protection, yet the people entirely abandoned their duty to guard God's sanctuary from impurity. Their primary responsibility was to protect the holy site, keep away the impure and uncircumcised, and ensure that only fit, decent, and holy priests were appointed to perform the sacred service [מצודת דוד, אברבנאל, מלבי״ם, שטיינזלץ].
Instead of fulfilling this duty, they committed an active offense. This was not merely a passive failure to stand watch; they took deliberate action and appointed others to take their place [מצודת ציון]. Rather than guarding the site themselves, they handed the responsibility over to strangers [מלבי״ם].
The identity of these newly appointed guards reveals the depth of the failure. Some suggest they were foreigners [מלבי״ם], or corrupt individuals and murderers who were entirely unfit for such a sacred role [רש״י, שטיינזלץ]. A primary approach among commentators, however, points to an even deeper betrayal: these guards were the very same people who had previously served as guards for the public during their idol worship [רד״ק, מצודת דוד, אברבנאל].
The severity of this act is amplified by the fact that the people made these improper appointments entirely on their own authority and for their own convenience, treating the guards as their personal agents [רש״י, מלבי״ם]. According to the perspective that connects these guards to idolatry, this highlights the ultimate desecration. The people took the exact individuals who guarded their houses of idol worship and brought them directly into the sanctuary of God [רד״ק, מצודת דוד, אברבנאל].