Prayers coinciding with that of angels results in forgiveness of sins:

- The Prophet (pbuh) said, "Say Amin" when the Imam says it and if the Amin of any one of you coincides with that of the angels then all his past sins will be forgiven." Ibn Shihab said, "Allah's Apostle used to Say "Amin."

Volume 1, Book 12, Number 747, Narrated Abu Huraira, See also 748
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If you recite a certain prayer and die that day, your sins will all be forgiven:

- The Prophet (pbuh) said "The most superior way of asking for forgiveness from Allah is: 'Allahumma anta Rabbi la ilaha illa anta, Anta Khalaqtani wa ana abduka, wa ana 'ala ahdika wa wa'dika mastata'tu, A'udhu bika min Sharri ma sana'tu, abu'u Laka bini'matika 'alaiya, wa Abu Laka bidhanbi faghfirli innahu la yaghfiru adhdhunuba illa anta." The Prophet added. "If somebody recites it during the day with firm faith in it, and dies on the same day before the evening, he will be from the people of Paradise; and if somebody recites it at night with firm faith in it, and dies before the morning, he will be from the people of Paradise."

Volume 8, Book 75, Number 318, Narrated Shaddad bin Aus, See also 335
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