鞭長莫及（鞭長莫及）　

◎ 鞭長莫及 biāncháng-mòjí

(1) [although the whip is long,it does not reach the horse‘s belly——cannot do it much as one would like do] 本意為馬鞭雖長,但打不到馬肚子上。喻雖有力,力量亦達(dá)不到

雖鞭之長,不及馬腹。——《左傳·宣公十五年》

(2) 后用以喻力不能及。亦作“鞭不及腹”