Quinn thinks very hard about killing him, since he promised Estes he would do it the second Carrie went into town for croissants and her Latisse prescription, but then doesn’t do it. Why not? Because you can see a person’s momentum or you can see their position, but never both at the same time. Quinn sees Brody on his knees, praying, and he looks very small. Whether or not he entirely intended to stab Nick through the hand that day, he saw what happened next: He saw Carrie break him apart and put him back together. He was there when Nick freaked out on Roya, and he was there when Carrie fucked his pieces back into human shape.
He came to trust Nick the same way he came to trust Carrie, through sheer pragmatism: Everything they ever said came true, all the way down the line. Nick may be a terrorist, and Carrie may be a nutcase, but that doesn’t change the fact that their promises and guesses and secrets and admissions always worked out in the end.
What Carrie was to Brody, last year, is what Quinn has become to them. He has crawled into bed with them, and listened to them telling secrets. He is not impressed by love, but he knows what honesty looks like. And now, with this prayer, he knows another secret that not even Carrie gets to know. I wanted it to be a transcendent moment in which Nick’s communion with God showed Quinn they were the same, but I don’t know if it got that far. I just know that when we are alone, that is when we are unafraid. It’s how Carrie fell in love, too.