Authentic Supplication Number 7.
And he said: “Whoever says, Subhana ‘allahi wa bihamdihi (8) 100 times a day, will be forgiven all his sins even if they were like the foam of the Sea.”
(8) Subhana ‘allah: honored is Allah from all things unsuitable to Him [“Glorified is Allah” is also used in this book for this phrase]. Wa bihamdihi: and [I am] in celebration of his Praise.
Reported in Saheeh ‘Al-Bukhari and Saheeh Muslim. ‘Al-Albani included this hadeeth in The Authentic of Good Sayings as #7.