间不容发

jiānbùróngfà

(1) [a seamless heavenly robe--flawless; by the skin of one's teeth; by a hair's breadth; the difference is as narrow as a hair's breadth]∶中间放置不下一根头发, 形容相距极微

律厤迭相治, 其间不容发。 --《大戴礼记》

(2) [the situation is extremely critical; within a hair of; within an inch of]∶比喻情势危急到极点

其出不出, 间不容发。 --汉·枚乘《上书谏吴王》