The Messenger of Allah ﷺ said, "Whoever says one hundred times in a day, 'There is no god but Allah alone, with no partner. To Him belongs the dominion, to Him belongs all praise. He gives life and causes death, and He has power over all things,' it will be equivalent to freeing ten slaves, one hundred good deeds will be recorded for him, one hundred sins will be erased from him, and it will be a protection for him from Satan that day until evening. No one will come with anything better than what he has brought, except someone who does more than that."With this same chain of narration, the Prophet ﷺ said, "Whoever says, 'Glory be to Allah and praise be to Him,' one hundred times, his sins will be wiped away, even if they were more than the foam of the sea."
حدثنا إسحق بن موسى الأنصاري حدثنا معن حدثنا مالك عن سمي عن أبي صالح
أن رسول الله ﷺ قال من قال لا إله إلا الله وحده لا شريك له له الملك وله الحمد يحيي ويميت وهو على كل شيء قدير في يوم مائة مرة كان له عدل عشر رقاب وكتبت له مائة حسنة ومحيت عنه مائة سيئة وكان له حرزا من الشيطان يومه ذلك حتى يمسي ولم يأت أحد بأفضل مما جاء به إلا أحد عمل أكثر من ذلك وبهذا الإسناد عن النبي ﷺ قال من قال سبحان الله وبحمده مائة مرة حطت خطاياه وإن كانت أكثر من زبد البحر
[Its chain of transmission is sahih]Reference: It is agreed upon (by Bukhari and Muslim), and Bukhari transmitted it in the Book of Supplications, Chapter on the Merit of Tahleel, hadith no. 6403, and Muslim, hadith no. 2691, from the hadith of Malik through this same route. It is also found in Muwatta 1/209 (Yahya's version), with a slight difference.