勿谓言之不预

(idiom) don't say you haven't been forewarned (threat used by the PRC in international diplomacy)

do not

surname Wei

to speak / to say / to name / to designate / meaning / sense

words / speech / to say / to talk

(possessive particle, literary equivalent of 的[de5]) / him / her / it

no; not so / (bound form) not; un-

to advance / in advance / beforehand / to prepare