It is narrated from Sayyiduna Abdullah bin Zubair that the Prophet (peace and blessings be upon him) said: A man swore a false oath with these words: "By Allah, besides whom there is no deity." So, by the blessing of reciting this word of Tawheed, all his sins are forgiven.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16101
Hadith Gradingحکم دارالسلام:إسناده ضعيف، وهذا الحديث من مناكير عطاء بن السائب