It is narrated from Hazrat Abu Sa'id Khudri (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "'Wail' is the name of a valley in Hell in which a disbeliever will tumble for forty years before reaching its depth. And 'Sa'ud' is the name of a mountain of fire upon which he will climb for seventy years, then fall down, and this process will continue forever."