SB 9.8.28
sri-bhagavan uvaca
asvo ’yam niyatam vatsa
pitamaha-pasus tava
ime ca pitaro dagdha
gangambho ’rhanti netarat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Personality of Godhead said: My dear Amsuman, here is the animal sought by your grandfather for sacrifice. Please take it. As for your forefathers, who have been burnt to ashes, they can be delivered only by Ganges water, and not by any other means.