Volsunga Saga - Chapter XVI: The Prophecy of Grifir Unknown Author (Ft. Translated by William Morris and Eirikr Magnusson)

There was a man hight Grifir, who was Sigurd's mother's brother, and a little after the forging of the sword Sigurd went to Grifir, because he was a man who knew things to come, and what was fated to men: of him Sigurd asked diligently how his life should go; but Grifir was long or he spake, yet at the last, by reason of Sigurd's exceeding great prayers, he told him all his life and the fate thereof, even as afterwards came to pass. So when Grifir had told him all even as he would, he went back home; and a little after he and Regin met.
Then said Regin, "Go thou and slay Fafnir, even as thou hast given thy word."

Sigurd said, "That work shall be wrought; but another is first to be done, the avenging of Sigmund the king and the other of my kinsmen who fell in that their last fight."