It is narrated from Hazrat Abu Dharr (may Allah be pleased with him) that he asked, "O Messenger of Allah! What is fasting?" The Noble Prophet (peace and blessings be upon him) said, "An obligation which is to be fulfilled."
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 21365
Hadith Gradingحکم دارالسلام:حسن لغيره، وهذا إسناد ضعيف لإبهام الراوي عن عوف بن مالك