Ya'akov Avinu never died. Ya'akov is compared to his descendants, as his offspring are alive, so too, he is alive. This passage is quite puzzling. Rebbi Yitzchak questions the assertion that Ya'akov is still alive, his burial serving as ample evidence. Let us explain.
Death is the ultimate defilement, a final barrier obscuring man's view of eternity.
It clouds our perception, limiting this world to mortal dimensions. Of necessity therefore, the Mitzva that teaches of this purification lies beyond our grasp, the Chok of Para Aduma. Ya'akov Avinu is the living embodiment of Parshas Parah. His life continues in a world beyond our reach. As the red heifer is a Mitzva that can never be fully understood, so too, the life of Ya'akov is eternally sustained, despite all logic.