Despite the warnings of Friar Laurence in Act II that "...violent delights have violent ends," Romeo, in his rage over the death of his friend Mercutio, slays Tybalt in Act III, Scene 1. Aware of the decree of the Prince, Benvolio explains to the Prince that in the confrontation Romeo spoke of love and peace but Tybalt was "deaf to peace" and killed Mercutio with "a martial scorn." Hearing this, the prince banishes Romeo from Verona.
When Friar Laurence learns of the misfortunes of Romeo, he instructs Romeo to stay in Mantua, and he will communicate with him through Romeo's servant, Balthasar, who will visit Romeo from time to time with news of Juliet. He tells Romeo,
Sojourn in Mantua. I'll find out your man,
And he shall signify from time to time
Every good hap to you that chances here. (3.3.170-173)
In the meantime, Friar Laurence will try to mediate between the two families, reveal the secret marriage of Romeo and Juliet, and convince the Prince to retract his banishment of Romeo.