tn The verb is a perfect tense with a vav (ו) consecutive; it and the preceding perfect tense follow the imperative, and so have either a force of instruction, or, as taken here, are the equivalent of an imperfect tense (of permission).
tn Now the imperfect tense negated is used; here the prohibition would fit (“they will not come near”), or the obligatory (“they must not”) in which the subjects are obliged to act—or not act in this case.