You should show the least vanity about your greatest gifts. Content yourself with doing: leave saying to others.

[Afecte menos sus mayores eminencias. Conténtese con hacer, y deje para otros el decir.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 295 (1647) [tr. Maurer (1992)]
    (Source)

(Source (Spanish)). Alternate translations:

Shew as little as thou canst thy most eminent qualities. Rest satisfied to doe, and leave it to others to talk of it.
[Flesher ed. (1685)]

The greater your exploits the less you need affect them: content yourself with doing, leave the talking to others.
[tr. Jacobs (1892)]

Real achievement needs no such affectation. Rest in accomplishment, and leave talk to others. Do, and do not brag.
[tr. Fischer (1937)]

Make the least ado about your greatest gifts. Be content to act, and leave the talking to others.
[Source]