In act 2, scene 4, the Nurse approaches Romeo to tell him that Juliet will meet him in order to get married. They make plans for the lovers to meet Friar Laurence at his church for their secret wedding. The Nurse goes on to warn Romeo that, owing to Juliet's young age, he must not mistreat his new bride in any way and must remain faithful to her. Otherwise, he would be doing a great evil.

But first let me tell ye, if ye should lead her into a fool’s paradise, as they say, it were a very gross kind of behavior, as they say. For the gentlewoman is young, and therefore, if you should deal double with her, truly it were an ill thing to be offered to any gentlewoman, and very weak dealing. (act 2, scene 4, 78-79).

At the very end of act 2, the Friar expresses his misgivings to Romeo about his relationship with Juliet. He is about to marry the two young lovers, but he is clearly worried that they are acting too quickly and impulsively. He tells Romeo that

These violent delights have violent ends

And in their triumph die, like fire and powder,

Which, as they kiss, consume. (act 2, scene 6, 9-11)