Abu Hurairah (RAA) narrated that the Messenger of Allah (ﷺ) said:
"Whoever says a hundred times, 'How perfect Allah is and I praise Him,' his sins will be forgiven though they may be as much as the foam of the sea." Agreed upon. (JA)
English reference (JA): Book 16, Hadith 1586 (JA)
Arabic reference (JA): Book 16, Hadith 1543 (JA)