Hǎode lǐngdǎo yīnggāi rènrén-wéixián, ér búshì rènrén-wéiqīn.
Good leaders should appoint people on merit, not on personal connections.
Tips
history
From the 《尚书·咸有一德》: 任官惟贤才 - 'Appoint officials only by their virtue and ability.' One of the earliest classical principles of Chinese governance.
mistakes
Almost always paired in contrast with its opposite 任人唯亲 ('appoint people based on personal connections'). Mixing them up reverses your meaning entirely.