R. Johanan was one of the last beautiful men of Jerusalem. Rish Lakish, a robber, surprised him in the bath thinking him to be a woman. He was converted to study on the promise of obtaining R. Johanan ’s sister as a wife. Once they were arguing about some legal point and the anger of R. Johanan caused Rish Lakish to die. The Rabbi grieved over it to his death.
The Robber Who Became a Sage and Broke His Teacher's Heart
Gaster, Exempla No. 224; Bava Metzia 84a