In Act 2, Scene 3, Romeo pays a visit to Friar Lawrence early in the morning to act Friar Lawrence to marry him and Juiet. Friar Lawrence is surprised to see Romeo at such an early hour and inquires as to whether Romeo is concerned about something.
"Care keeps his watch in every old man's eye,/And where care lodges, sleep will never lie" (2.3.37-38).
Romeo replies that nothing is troubling him, and afer he tells Friar Lawrence that he has not been to bed, Friar Lawrence presumes he has been with Rosaline. Once Romeo informs the Friar that he was with Juliet, the Friar is surprised and confused. "Holy Saint Francis, what a change is here!" (2.3.78). After getting over his shock of the news, the Friar agrees to marry the two because he believes the marriage will end the feud between the Montagues and the Capulets. He says,
"In one respect I'll thy assistant be,/For this alliance may so happy prove/To turn your households' rancor to pure love" (2.3.97-99).
Before Romeo leaves, the Friar advises Romeo to take his time with the relationship because, "They stumble that run fast" (2.3.101).