Tā měiwǎn fǎnxǐng, wèn zìjǐ yǔpéngyǒujiāo'érbùxìnhū.
Every evening he reflects, asking himself 'in dealings with friends, have I failed to be trustworthy?'
Tips
history
From 《论语·学而》 (Analects, Xue'er 1:4), the famous 三省 (three self-examinations) of 曾子 (Zengzi, Confucius' disciple): 吾日三省吾身：为人谋而不忠乎？与朋友交而不信乎？传不习乎？ (I daily examine myself on three things: in planning for others, have I been less than loyal? In dealings with friends, have I been less than trustworthy? Have I failed to practice what was transmitted to me?). A cornerstone of Confucian self-cultivation.
usage
乎 is a classical question particle (≈ 吗). 信 here = trustworthy, keeping one's word (not 'believe'). Always part of the three-question set. Chinese elementary moral education still teaches this passage as the model of daily reflection.
