Recorded in Yuan-dynasty playwright Ji Junxiang's 赵氏孤儿 (Zhào shì gū'ér, 'The Orphan of Zhao'): 程婴，我一言已定，你再不必多疑了 — 'Cheng Ying, my word is given; you need not doubt any further.' Used colloquially today the same way as 'shake on it' in English.
usage
Conversational. Often spoken as a closer when sealing a casual agreement, frequently followed by 击掌 (jīzhǎng, 'high five') in modern use.
