لَمَّا خَرَجَ الْمَأْمُونُ مِنْ خُرَاسَانَ يُرِيدُ بَغْدَادَ وَ خَرَجَ الْفَضْلُ ذُو الرِّئَاسَتَيْنِ وَ خَرَجْنَا مَعَ أَبِي الْحَسَنِ ع وَرَدَ عَلَى الْفَضْلِ بْنِ سَهْلٍ ذِي الرِّئَاسَتَيْنِ كِتَابٌ مِنْ أَخِيهِ الْحَسَنِ بْنِ سَهْلٍ وَ نَحْنُ فِي بَعْضِ الْمَنَازِلِ إِنِّي نَظَرْتُ فِي تَحْوِيلِ السَّنَةِ فِي حِسَابِ النُّجُومِ فَوَجَدْتُ فِيهِ أَنَّكَ تَذُوقُ فِي شَهْرِ كَذَا وَ كَذَا- يَوْمَ الْأَرْبِعَاءِ حَرّ
“When al-Ma’mun left Khurasan for Baghdad along with him came Fadl, Dhu al-Al-Ri’asatayn and we came out with abu al-Hassan (a.s.) Fadl ibn Sahl had received a letter from his brother Hassan, while we were on our journey. Hassan had said in the letter, “I studied the Zodiac changes this year according to the astrologic