避其锐气，击其惰归 避其銳氣，擊其惰歸 bì qí ruì qì , jī qí duò guī avoid the enemy when he is fresh and strike him when he is tired and withdraws (idiom)
金玉其外，败絮其中 金玉其外，敗絮其中 jīn yù qí wài , bài xù qí zhōng gilded exterior, shabby and ruined on the inside (idiom)
金玉其表，败絮其中 金玉其表，敗絮其中 jīn yù qí biǎo , bài xù qí zhōng gilded exterior, shabby and ruined on the inside (idiom)
兄弟阋于墙，外御其侮 兄弟鬩於墻，外禦其侮 xiōng dì xì yú qiáng , wài yù qí wǔ internal disunity dissolves at the threat of an invasion from outside (idiom)
知其然而不知其所以然 zhī qí rán ér bù zhī qí suǒ yǐ rán (saying) to know that it is so but not why it is so
工欲善其事，必先利其器 gōng yù shàn qí shì , bì xiān lì qí qì To do a good job, an artisan needs the best tools (idiom). Good tools are prerequisite to the successful execution of a job
以其人之道，还治其人之身 以其人之道，還治其人之身 yǐ qí rén zhī dào , huán zhì qí rén zhī shēn 1. to use an opponent's own methods to obtain retribution (idiom, from Song dynasty neo-Confucianist Zhu Xi 朱熹[zhū xī])2. to get revenge by playing sb back at his own game; to give sb a taste of his own medicine
variant of 沙琪玛[shā qí mǎ]
八仙过海，各显其能 八仙過海，各顯其能 bā xiān guò hǎi , gè xiǎn qí néng see 八仙過海，八仙过海，各显神通[bā xiān guò hǎi gè xiǎn shén tōng]
(literary) (similar to 多么[duō me], used before an adjective in exclamations) how (fortunate etc); so (many etc)