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]. (ID)
App reference (ID): Book 9, Hadith 265 (ID)
Arabic/English book reference (ID): Book 9, Hadith 1255 (ID)