Maester Aemon?
"The Dothraki believe the stars are the spirits of the valiant dead."
At first I was wondering if it was a song a little bird sang to a dog and was going to go with said little bird.Here's a hint. It's a POV character. That narrows the list considerably.
So, just for giggles, it sounds a bit like something Tyrion might say when scheming.Both of these reveal the minds of fighters who have anticipated death in battle.
"The Dothraki believe the stars are the spirits of the valiant dead."
The crows came in the blue dusk with the evening stars. "The Dothraki believe the stars are the spirits of the valiant dead," Theon said. Maester Luwin had told him that, a long time ago.
Theon, it rhymes with crayon....