It is narrated from Hazrat Thawban (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Whoever fasts in the month of Ramadan, it will be equal to ten months, and by fasting six days after Eid al-Fitr, the reward will be as if he has fasted for the whole year.
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 22412
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن