Péngyǒu qǐchéng shí, tā yǐnyòng tiānxiàshéirénbùshíjūn lái gǔlì tā.
As his friend set out, he quoted 'who under heaven does not know you' to encourage him.
Tips
history
From Gao Shi's (高适, Tang dynasty) 《别董大》 (其一): 千里黄云白日曛，北风吹雁雪纷纷。莫愁前路无知己，天下谁人不识君 - 'yellow clouds for a thousand li dim the white sun; the north wind drives geese through thickening snow. Do not worry there are no friends ahead - who under heaven does not know you?' A farewell to the famous qin-player Dong Tinglan (董庭兰).
usage
君 here is a respectful 'you,' not 'lord.' 识 = 'to know / recognize.' Almost always quoted with its setup 莫愁前路无知己. One of the most-cited farewell couplets in Chinese, still used at graduations and retirements.
