عن أبي قتادة رضي الله عنه أن رسول الله صلى الله عليه وسلم‏:‏ سئل عن صوم يوم الاثنين فقال‏:‏ ‏"‏ذلك يوم ولدت فيه، ويوم بعثت أو أنزل علي فيه‏"‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏

Abu Qatadah (May Allah be pleased with him) reported

The Messenger of Allah (ﷺ) was asked about fasting on Mondays. He said, "That is the day on which I was born and the day on which I received Revelation."[Muslim].