صحيح مسلم
Sahih Muslim
كتاب الصيام
The Book of Fasting
باب اسْتِحْبَابِ صِياَمِ ثَلاَثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ وَصَوْمِ يَوْمِ عَرَفَةَ وَعَاشُورَاءَ وَالاِثْنَيْنِ وَالْخَمِيسِ.
Chapter: It is recommended to fast three days of every month, and to fast on the days of 'Arafah and 'Ashura', and to fast on Mondays and Thursdays
Hadith 1162
This hadith is listed as number 2750 in Maktaba Shamila
وحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ ، حَدَّثَنَا مَهْدِيُّ بْنُ مَيْمُونٍ ، عَنْ غَيْلَانَ ، عَنْ عَبْدِ اللَّهِ بْنِ مَعْبَدٍ الزِّمَّانِيِّ ، عَنْ أَبِي قَتَادَةَ الْأَنْصَارِيِّ رَضِيَ اللَّهُ عَنْهُ : أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ " سُئِلَ عَنْ صَوْمِ الِاثْنَيْنِ " ، فَقَالَ : " فِيهِ وُلِدْتُ ، وَفِيهِ أُنْزِلَ عَلَيَّ " .
Abu Qatadah (RA) Ansari (RA) reported that Allah's Messenger (ﷺ) was asked about fasting on Monday, whereupon he said: It is (the day) when I was born and revelation was sent down to me.
