Even in business, the gentleman reckons by righteousness - you can't think only about money.
Tips
history
From 《论语·里仁》 (Analects: Li Ren). Confucius says: 君子喻于义,小人喻于利 - 'the gentleman is moved by righteousness; the petty person is moved by profit.' A classic formulation of the Confucian moral divide between 义 (duty/rightness) and 利 (gain).
usage
喻 here means 'to be enlightened by / to comprehend via' - a slightly archaic usage. 于 is the classical preposition 'by / at.' Almost always quoted with its pair 小人喻于利.