There are two firemen who went to quench a fire near the ocean. After the fire has been extinguished, they both went to the water to clean themselves.One of them had a charcoal on his face while the other had a clean face. 

Which fireman do you think will wash his face first?

…

The one who had a clean face. Why? 

It’s because when he saw the dirt on the other man’s face, he washed his face. He assumed he had it on his face as well. 
And when the other man saw him washing his face, he realized he should do the same.

(Photo grabbed from Google)