It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever fasts Ramadan and then follows it with six days of Shawwal comes out of his sins (purified) like the day his mother gave birth to him."
Imam al-Tabarani (may Allah have mercy on him) said: "Only Abu Abdullah al-Himsi narrated this hadith from Nafi', and Maslamah bin Ali is alone in narrating it from him."
Hadith Referenceالمعجم الأوسط / باب الميم / 8622
Hadith Gradingمحدثین:إسناده ضعيف لضعف مسلمة بن علي الخشني
Hadith Takhrij«قال الهيثمي: فيه مسلمة بن علي الخشني وهو ضعيف «مجمع الزوائد ومنبع الفوائد، ج 3، ص 184»»