Chapter on the Recommended Fasts of the Year
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 4
وَ فِي رِوَايَةِ عَبْدِ اَللَّهِ بْنِ سِنَانٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: «إِنَّ رَسُولَ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ سُئِلَ عَنْ صَوْمِ خَمِيسَيْنِ بَيْنَهُمَا أَرْبِعَاءُ فَقَالَ «أَمَّا اَلْخَمِيسُ فَيَوْمٌ تُعْرَضُ فِيهِ اَلْأَعْمَالُ وَ أَمَّا اَلْأَرْبِعَاءُ فَيَوْمٌ خُلِقَتْ فِيهِ اَلنَّارُ وَ أَمَّا اَلصَّوْمُ فَجُنَّةٌ ».
In the narration of Abdullah ibn Sinan from Abu Abdullah (Imam Jafar ibn Muhammad Al-Sadiq عليه السلام), he said: "The Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) was asked about fasting on two Thursdays with a Wednesday in between. Imam عليه السلام said: 'As for Thursday, it is the day on which deeds are presented. As for Wednesday, it is the day on which the Fire was created. And fasting is a shield.'"
- Ṣaḥīḥ al-Faqīh