Sayyiduna Abd al-Rahman bin Dalham (may Allah be pleased with him) narrates: A man said: O Messenger of Allah! Teach me a deed by which I may enter Paradise. The Prophet (peace and blessings be upon him) said: Do not become angry, and you will have Paradise. He said: O Messenger of Allah! Tell me something more! The Prophet (peace and blessings be upon him) said: Seek forgiveness from Allah Almighty seventy times in the day before the sun sets, and Allah Almighty will forgive your sins of 70 years. He said: I do not have seventy years of sins. The Prophet (peace and blessings be upon him) said: Then your father's (sins too will be forgiven). He said: My father does not have seventy years of sins either. The Prophet (peace and blessings be upon him) said: Then your household's (sins will be forgiven). He said: My household does not have seventy years of sins either. The Prophet (peace and blessings be upon him) said: Then your neighbours' (sins will be forgiven).
Al-Tabarani recorded it, and its chain contains a narrator whom I do not know.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب التوبة / 17588