VERBS, AUXILIARY. Do omitted before notVerbs: "Do" omitted before "Not." In Early English the tenses were represented by their inflections, and there was no need of the auxiliary "do." As the inflections were disused, "do" came into use, and was frequently employed by Elizabethan authors. They, however, did not always observe the modern rule of using the auxiliary whenever not precedes the verb. Thus--
“Whereof the ewe not bites.” Ib. v. 1. 38.
“I not doubt.
“It not appears to me.” Ib. 107. “Hear you bad writers and though you not see.” BEAUMONT on B. J.
“It not belongs to you.
“Neat Terence, witty Plautus, now not please.” B. J. on Shakespeare. Less commonly in a subordinate sentence
“On me whose all not equals Edward's moiety.
Later, a rule was adopted that either the verb, or the auxiliary part of it, must precede the negative: "I doubt not," or "I do not doubt." Perhaps this may be explained as follows. The old English negative was "ne." It came before the verb, and was often supplemented by a negative adverb "nawicht," "nawt," "noht" (which are all different forms of "no whit" or "naught"), coming after the verb. “His hors was good, but he ne was not gaie.” CHAUCER, C. T. 74. (Compare in French "ne . . . pas," in Latin, "non (nenu)," i.e. "ne . . . unum.") In the fifteenth century (Mätzner) this reduplication began to pass out of fashion. In Shakespeare's time it had been forgotten; but, perhaps, we may trace its influence in the double negative "nor will not," &c., which is common in his works.
“I beseech you . . . that you not delay.
Possibly the idiom now under consideration is also a result of the Early English idiom. The not, which had ousted the old dual negative "ne" . . . "not," may have been thought entitled to a place either before or after the verb. Latin, moreover, would tend in the same direction. It must further be remembered that not is now less emphatic than it was, when it retained the meaning of "naught" or "no-whit." We can say, "I in-no-way trust you," or, perhaps, even "I no-whit trust you," but not is too unemphatic to allow us to say "I not trust you." Hence the "do" is now necessary to receive a part of the emphasis. Not is sometimes found in E. E. and A.-S. between the subject and the verb, especially in subordinate sentences where the not, "no-whit," is emphatic.
“Vex not yourself, nor strive not with your breath.