Wallace’s grammar has a good section on the Aorist Imperative, see below.
The idea that aorist must be in some sense past referring is not correct. This form can be ingressive and signal the start of an action, but not in your verse as that makes no sense contextually. Here is stresses the urgency of the request. And, while this is not a completed action, it could have been going on for a while already.
2. Aorist Imperative ExSyn 719–21
The basic idea of the aorist imperative is a command in which the action is viewed as a whole, without regard for the internal make-up of the action. However, it occurs in various contexts in which its meaning has been affected especially by lexical or contextual features. Consequently, most aorist imperatives can be placed into one of two broad categories, ingressive or constative . Further, the aorist is most frequently used for a specific command rather than a general precept (usually the domain of the present)
This is a solemn or categorical command. The stress is not “begin an action,” nor “continue to act.” Rather, the stress is on the solemnity and urgency of the action; thus “I solemnly charge you to act—and do it now!” This is the use of the aorist in general precepts. Although the aorist is here transgressing onto the present tense’s turf, it adds a certain flavor. It is as if the author says, “Make this your top priority.” As such, the aorist is often used to command an action that has been going on. In this case, both solemnity and a heightened urgency are its force.
 The difference between the aorist and the future indicative in such general precepts
seems to be that the aorist is used for a sense of urgency while the future indicative does not
stress this element.