The 67th prohibition is that we are forbidden from omitting the guarding of the Holy Temple and patrolling it constantly each night.
The source of this mitzvah is G‑d's statement,1 "They should guard the Sanctuary [...so that there not be any more Divine wrath directed at the Israelites.]"
We have already explained in Positive Commandment 22 that guarding and patrolling the Holy Temple is a positive mitzvah. Similarly here we explain that its omission constitutes a prohibition.
The Mechilta says, "The verse2 'They shall guard the Ohel Moed,' is only a positive commandment. What verse provides the prohibition? The verse 'They should guard the Sanctuary [...so that there not be any more Divine wrath directed at the Israelites].' "
The details of this mitzvah are explained in the beginning of tractates Tamid and Middos.
