What are some quotes from Friar Laurence that indicate his loyalty to Romeo?

In Act 2, Scene 3, when Romeo tells Friar Lawrence he hasn't been to bed yet, the friar says, "God pardon sin! Wast thou with Rosaline?"

The fact that Lawrence knows Romeo so well is something that lays the foundation for loyalty. So does the fact that his response starts with forgiveness rather than judgment.

Likewise, when he listens to Romeo talk and talk about how he now loves Juliet in that same scene, Lawrence chides him for changing quickly, but doesn't really judge him harshly.

In Act 2, Scene 6, Lawrence speaks kindly to Juliet, saying, "Romeo shall thank thee, daughter, for us both." This shows loyalty by aligning Lawrence's fate with Romeo.

You can really see loyalty starting in Act 3, Scene 3, when Lawrence keeps Romeo from killing himself. These lines start with "Hold thy desperate hand!"

In that same scene, Lawrence chides Romeo for how he changes who he loves, saying "Holy Saint Francis, what a change is here!
Is Rosaline, whom thou didst love so dear,
So soon forsaken? young men's love then lies

Not truly in their hearts, but in their eyes."

However, despite judging Romeo for this change, he soon thereafter offers to help him, saying, "But come, young waverer, come, go with me,
In one respect I'll thy assistant be;"

If you disagree with someone's actions, but help them anyway, that's a sign of loyalty.