The Collaborative International Dictionary of English v.0.48:

Precept \Pre"cept\, v. t.
   To teach by precepts. [Obs.] --Bacon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Precept \Pre"cept\, n. [L. praeceptum, from praecipere to take
   beforehand, to instruct, teach; prae before + capere to take:
   cf. F. pr['e]cepte. See Pre-, and Capacious.]
   1. Any commandment, instruction, or order intended as an
      authoritative rule of action; esp., a command respecting
      moral conduct; an injunction; a rule.
      [1913 Webster]

            For precept must be upon precept.     --Isa. xxviii.
                                                  10.
      [1913 Webster]

            No arts are without their precepts.   --Dryden.
      [1913 Webster]

   2. (Law) A command in writing; a species of writ or process.
      --Burrill.
      [1913 Webster]

   Syn: Commandment; injunction; mandate; law; rule; direction;
        principle; maxim. See Doctrine.
        [1913 Webster]

WordNet (r) 3.0 (2006):

precept
    n 1: rule of personal conduct [syn: principle, precept]
    2: a doctrine that is taught; "the teachings of religion"; "he
       believed all the Christian precepts" [syn: teaching,
       precept, commandment]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "precept":
   a belief, adage, ana, analects, aphorism, apophthegm, apothegm,
   article of faith, axiom, behest, bench warrant, bidding, byword,
   canon, capias, catchword, caveat, charge, code, collected sayings,
   commandment, current saying, death warrant, decree, decretum,
   dictate, dictum, direction, directive, distich, doctrine, dogma,
   edict, epigram, expression, fiat, fieri facias, fundamental,
   general orders, gnome, golden saying, guide, guideline,
   habere facias possessionem, injunction, instruction, interdict,
   law, mandamus, mandate, mandatory injunction, maxim, mittimus,
   moral, mot, motto, nisi prius, notice, notification, oracle, order,
   ordinance, phrase, pithy saying, prescript, prescription,
   principle, process, prohibitory injunction, proverb,
   proverbial saying, proverbs, regulation, rule, saw, saying,
   search warrant, sentence, sententious expression, slogan, sloka,
   statute, stock saying, sutra, teaching, tenet, text, ukase,
   unwritten law, verse, warrant, warrant of arrest,
   warrant of attorney, wisdom, wisdom literature, wise saying,
   witticism, word, words of wisdom, writ



Bouvier's Law Dictionary, Revised 6th Ed (1856):

PRECEPT. A writ directed to the sheriff or other officer, commanding him to
do something. The term is derived from the operative praecipimus, we
command.