trih-saptabhih pita putah
sri-bhagavan uvaca-the Supreme Personality of Godhead said; trih-saptabhih-seven multiplied by three (that is to say, twenty-one); pita-father; putah-purified; pitrbhih-with your forefathers; saha-all together; te-your; anagha-O most sinless personality (Prahlada Maharaja); yat-because; sadho-O great saintly person; asya-of this person; kule-in the dynasty; jatah-took birth; bhavan-you; vai-indeed; kula-pavanah-the purifier of the whole dynasty.