Steal The Firewood From Under the Pot (釜底抽薪) from the Thirty-Six Stratagems (三十六計)

釜底抽薪

不敵其力，而消其勢，兌下乾上之象。

"When faced with an enemy too powerful to engage directly you must first weaken him by undermining his foundation and attacking his source of power."

Quoted from Chinese Classics and Translations

Excerpt from Important Explanations for the Accomplishment of the Thirteen Postures (十三勢行功要解) by Wǔ Yǔxiāng (武禹襄)

先在心,後在身,腹鬆淨,氣歛入骨,神舒體靜,刻刻存心. 切記一動無有不動,一靜無有不靜.

武禹襄

"First the intention, then the body; the abdomen is completely relaxed; the Qi condenses into the bone; the Spirit is comfortable and the body is calm; this should be engraved in one’s mind. One shall remember that if one part moves, nothing remains immobile; if one part is still, there is nothing that moves."

By Wǔ Yǔxiāng (武禹襄), based on the translation by Yang Jwing Ming (楊俊敏) presented in the book Tai Chi Secrets of the Wu & Li Styles (太極拳武李氏先哲秘要) and various translations on the internet.