keep one's powder dry

Idioms  

1. Stay alert, be careful, as in Go ahead and take on the opposition, but keep your powder dry. This colloquial expression, which originally alluded to keeping gunpowder dry so that it would ignite, has been used figuratively since the 1800s but today is less common than take care.

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Example Sentences

It was a time, if ever there was one, to trust in Raffles and keep one's powder dry; and to that extent I may say I played the game.

From Mr. Justice Raffles by Hornung, E. W. (Ernest William)