From the scene in Order of the Phoenix when Harry sees the school-age Marauders via Pensieve. Okay, we all knew Viria was amazing, but she really outdid herself with this one. It doesn't hurt that this is one of my favorite Marauders scenes, either. :)
I really love this moment in the books. I don't think Dumbledore was trying to make Harry feel better, I think he genuinely thought Harry had become a good, brave man and Dumbledore truly felt better he had such a companion, especially in the light of the "suicide" he was about to do.