Sir, it's a bad policy to stay near a tree in a thunderstorm. It attracts the bolts.

6 seconds sound clip from the Waterloo (1970) movie soundboard.

You can hear this line at 01:43:04.101 in the Blu-ray version of the movie.

Quote context

[...]

- A hard pounding, gentlemen.

- Yes, sir.

- Lord Hay, take yourself for a run. General Lambert will retire 100 paces between the reverse slopes.

- But, Your Grace...

- Do as you're told, sir!

- General order. The army will retire a hundred paces.

- The army will retire 100 paces!

- The 27th will take position behind the Gordons!

- Sir, it's a bad policy to stay near a tree in a thunderstorm. It attracts the bolts.

- I'll take your impudent advice.

(CANNON FIRE)

- Wellington's retreating! Wellington's retreating! Nillion, follow me!

- Trumpeter, sound the advance! Charge!

[...]