You don't have to be a Triangle to Teach Geometry

Rabban Gamliel took a bath the night after his wife died.

His students said to him: "Rabbi, you taught us that a mourner is not allowed to bathe."

He replied: "I am not like other people.  I am a Jewish Prince."

And when Rabban Gamliel's slave Tavi died, Rabban Gamliel accepted condolences.

His students said to him: "Rabbi, you taught us that one may not accept condolences for a slave."

He replied: "Tavi was not like other slaves.  He was an honorable man."

(Brachot 16b)