328. The Aorist Imperative is very rarely used with μή: examples are
Il. 4.410 τῷ μή μοι πατέρας ποθʼ ὁμοίῃ ἔνθεο τιμῇ
Od. 24.248 σὺ δὲ μὴ χόλον ἔνθεο θυμῷ
Il. 18.134 σὺ μὲν μή πω καταδύσεο μῶλον Ἄρηος
Od. 16.301 μή τις ἔπειτʼ Ὀδυσῆος ἀκουσάτω
Il. 16.200 μὴ . . . λελαθέσθω
For the rule which is the complement of this one, forbidding the use of the present subjunctive with μὴ, see § 278 fin.
Regarding the origin of this curious idiom a very probable conjecture has been made by Delbürck (Synt. Forsch. iv. p. 120). In the Veda it has been shown by Grassmann that the prohibitive particle mâ is never found with the forms of the imperative proper, but only with the so-called "spurious conjunctive" or "injunctive." Hence it may be inferred that the imperative was only used originally in positive commands, not in prohibitions. Again, it appears that in Sanskrit the imperative is nearly confined to the present tense, and in Greek the forms of the 1st aorist imperative (κλέψον, middle κλέψαι) are certainly of late origin. The fine distinction which is made, in the imperative as well as in other moods, between the continuous action expressed by the present stem and the momentary action expressed by the aorist belongs to the specific development of Greek. Accordingly Delbrück suggests that the extension of the imperative to express prohibition took place at a time when the aorist imperative had not come into general use; hence it was only carried into the present tense. In other words, the form μή κλέπτε came into use in pre-historic Greek as an extension of the positive κλέπτε, and superseded μὴ κλέπτῃς, but μὴ κλέψῃs kept its ground, because the form κλέψοv did not then exist. This account of the idiom seems much more probable than any attempt to explain it on psychological grounds.