Sarah J. Maas said this quote

She realized that Rowan saw each of those thoughts and more as he reached into his tunic and pulled out a dagger. Her dagger. He extended it to her, it's long blade gleaming as if he'd been secretly polishing and caring for it these months.And when she grasped the dagger, it's weight lighter than she remembered, Rowan looked into her eyes, into her very core of her, and said, 'Fireheart'.