Zigong asked how to practice humanity. The Master said: “A craftsman who wishes to do good work must first sharpen his tools. In whatever country you settle, offer your services to the most virtuous ministers, and befriend those gentlemen who cultivate humanity.”

Confucius (551-479 BC) Chinese philosopher [Ku'ng Ch'iu / King Qiu, Ku'ng Fu-tzu / Kong Fuzi]
The Analects [Lun Yü], 15.10 (6th C. BC) [ed. Lao-Tse; tr. Leys (1997)]
    (Source)

Alt. trans.:

• 'Tsze-kung asked about the practice of virtue. The Master said, "The mechanic, who wishes to do his work well, must first sharpen his tools. When you are living in any state, take service with the most worthy among its great officers, and make friends of the most virtuous among its scholars."' [tr. Legge (1861), 15.9]
• 'Zigong asked about the practice of humaneness. The Master said, "Artisans who wish to excel at their craft must sharpen their tools. When you live in any given state, you should serve the worthiest among the counselors and befriend the most human among the educated professionals."'[tr. Annping Chin (1983)]
• Part of this is often quoted, without citation: "The expectations of life depend upon diligence; the mechanic that would perfect his work must first sharpen his tools." The quote can be found in English as early as the late 19th Century.