Rav Sheinberg asked someone who was going to the US,to bring him back a certain brand of soap.
he didn’t manage to get it ,so he brought him back a different brand.
R Sheinberg said-this is not what i asked you for.
The talmid couldn’t understand why R Sheinberg cared about the soap,until he explained that the brand of soap that he asked for,had a lather that washed off very quickly,so he wasted less time in the shower.