It was narrated to us by Moammed bin Amed al-Sināni al-Mukattib رحمه الله, who said – it was narrated to us by Moammed ibn Abī ʿAbd Allāh al-Kūfi, who said – it was narrated to us by Mūsa bin ʿImrān al-Najafi, from his uncle al-ussain bin Yazīd, from ʿAlī bin Sālim, from his father, who said:

I entered upon al-Ṣādiq, Jaʿfar bin Moḥammed عليهما السلام during [the month of] Rajab with a few days of it remaining. When he looked upon me, he said: “Oh Sālim, did you fast during this month at all?”
I said: “No, by Allāh, oh son of The Messenger of Allāh.”
He said to me: “Then indeed you have missed out on a great reward, that none knows its sum except Allāh, Might and Majestic. Indeed, this month has been favoured by Allāh, and its sanctity glorified. He has made obligatory its noblesness for those who fast.”
He said: So I said to him: “Oh son of The Messenger of Allāh, if I fast from the days that remain, will I be victorious in with a portion of the reward of those who fast in it?”
He said: “Oh Sālim, who ever fasts a day from the end of this month, it will be a security for him from the intense intoxication of death, and a security for him from the horror of the rise and punishment in the graves.
“Whoever fasts two days from the end of this month, there will be for him a permit upon the bridge (al-irā).
“Whoever fasts three days from the end of this month, he will be secure on the Day of The Greatest Dread from its horror and intensity, and will be given an absolution from the fire.

حدثنا محمد بن أحمد السناني المكتب (رحمه الله)، قال: حدثنا محمد ابن أبي عبد الله الكوفي، قال: حدثنا موسى بن عمران النخعي، عن عمه الحسين بن يزيد، عن علي بن سالم، عن أبيه، قال: دخلت على الصادق جعفر بن محمد (عليهما السلام) في رجب وقد بقيت منه أيام، فلما نظر إلي قال لي: يا سالم، هل صمت في هذا الشهر شيئا؟ قلت: لا والله يا بن رسول الله. فقال لي: لقد فاتك من الثواب ما لم يعلم مبلغه إلا الله عز وجل، إن هذا شهر قد فضله الله وعظم حرمته، وأوجب للصائمين فيه كرامته. قال: فقلت له: يا بن رسول الله، فإن صمت مما بقي شيئا، هل أنال فوزا ببعض ثواب الصائمين فيه؟ فقال: يا سالم، من صام يوما من آخر هذا الشهر، كان ذلك أمانا له من شدة سكرات الموت، وأمانا له من هول المطلع وعذاب القبر، ومن صام يومين من آخر هذا الشهر، كان له بذلك جواز على الصراط، ومن صام ثلاثة أيام من آخر هذا الشهر، أمن يوم الفزع الأكبر من أهواله وشدائده، وأعطي براءة من النار