Mu'jam Kabir Tabarani 11572 — the Prophet ﷺ said to Sayyiduna Abbas: O

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said to Sayyiduna Abbas (may Allah be pleased with him): "O my uncle! Shall I not teach you? Shall I not give you a gift? Shall I not inform you? Shall I not tell you ten qualities which, if you do them, Allah will forgive all your sins: the first and the last, the old and the new, the hidden and the open, the small and the great, those done by mistake and those done deliberately? (It is this:) You pray four rak'ahs, and in each rak'ah recite Surah al-Fatihah along with a surah. When you finish the recitation in the first rak'ah, say fifteen times while standing: 'Subhan Allah, wal-hamdu lillah, wa la ilaha illallah, wallahu akbar' (Glory be to Allah, praise be to Allah, there is no god but Allah, and Allah is the Greatest). Then bow and say it ten times while bowing. Then raise your head and say it ten times while standing. Then prostrate and say it ten times in prostration. Then raise your head and say it ten times while sitting. Then prostrate and say it ten times. Then raise your head and say it ten times. That makes seventy-five (in all). Repeat this in four rak'ahs. Then even if your sins were like the foam of the sea or the sand of 'Alij, Allah would forgive them for you."