 أَبِی ره قَالَ حَدَّثَنِی سَعْدُ بْنُ عَبْدِ اللَّهِ قَالَ حَدَّثَنِی أَحْمَدُ بْنُ الْحَسَنِ بْنِ الصَّقْرِ عَنْ أَبِی طَاهِرٍ مُحَمَّدِ بْنِ حَمْزَهَ بْنِ الْیَسَعِ عَنِ الْحَسَنِ بْنِ بَکَّارٍ عَنْ أَبِی الْحَسَنِ الرِّضَا ع قَالَ: بَعَثَ اللَّهُ مُحَمَّداً ص لِثَلَاثٍ مَضَیْنَ مِنْ شَهْرِ رَجَبٍ فَصَوْمُ ذَلِکَ الْیَوْمِ کَصَوْمِ سَبْعِینَ عَاماً. قال سعد بن عبد الله کان مشایخنا یقولون إن ذلک غلط من الکاتب و هو أنه لثلاث لیال بقین من رجب
5. My father (rah) said: it was narrated to me by Sa’d b. Abdillah who said it was narrated to me by Ahmad b. al-Hassan b. al-Saqr from Abi Tahir Muhammad b. Hamzah b. al-Yasaa’ from al-Hassan b. Bakkar from Abi al-Hassan al-Ridha  who said: “The Almighty Allah appointed Muhammad (s.a.w.s.) as His Apostle after three nights of the month of Rajab had passed. Hence observing fast on this day has reward equal to fasting seventy years.” Saad bin Abdullah says that according to our elders, there is a mistake and the real saying is that Allah appointed him as apostle when three nights were left in the month of Rajab.