A man asked Imam Ja`far as-Sadiq [a] said, "May I be your sacrifice! Why were the descendants of al-Husayn preferred over the descendants of al-Hasan when they came from the same line?"
So the Imam said: I will show you, so take it.
Surely, Gabriel [a] came down to Muhammad (s) before al-Husayn had been born, and he said to him, "A boy will be born to you who will be killed by your Umma after you."
So he (s) said, "O Gabriel, I do not need this."
He addressed him three times, then he called for `Ali, and he said to him, "Surely, Gabriel [a] informs me from Allah that a boy will be born to you who will be killed by your Umma after you."
So he [a] said, "I do not need this, O Messenger of Allah."
So he addressed `Ali [a] three times. Then, he said, "The Imamate, the inheritance, and the treasury will come through his descendants."
So he sent for Fatima [a], [saying,] "Allah brings you glad tidings of a boy who will be killed by my Umma after me."
So Fatima said, "I do not need this, O father."
So he (s) addressed her three times. Then, he sent to her, [saying,] "Certainly, surely, the Imamate, the inheritance, and the treasury will be in him."
So she said, "I am pleased with Allah."
So she conceived and became pregnant with al-Husayn. She was pregnant for six months, then gave birth to him - and no infant of six months ever lives except for al-Husayn b. `Ali and Jesus the son of Mary [a]. So Umm Salama took responsibility of him, and the Messenger of Allah would meet him every day and put his tongue in the lips of al-Husayn [a], and he would suckle it until he would recite [knowledge], and Allah would give him meat (laHm) from the meat of the Messenger of Allah (s). He would not suckle milk from Fatima [a] or from anyone else.
So when Allah revealed this regarding it, 'and her bearing him and his utter dependence on her took thirty months, and so, when he attains to full maturity and reaches forty years, he prays: O my Sustainer! Inspire me so that I may forever be grateful for those blessings of Yours with which You have graced me and my parents, and that I may do what is right that will meet with Your goodly acceptance; and grant me righteousness in my offspring.' (46:15) were he to have said, 'rectify for me my offspring', then all of them would have been Imams - however, he specified it in this way.
حدثنا احمد بن الحسن رحمه الله قال: حدثنا احمد بن يحيى قال: حدثنا
بكر بن عبد الله بن حبيب قال: حدثنا تميم بن بهلول قال: حدثنا علي بن حسان الواسطي عن عبد الرحمان بن كثير الهاشمي قال: قلت لابي عبد الله " ع " جعلت فداك من اين جاء لولد الحسين الفضل على ولد الحسن وهما يجريان في شرع واحد فقال لا أريكم تأخذون به، ان جبرئيل " ع " نزل على محمد صلى الله عليه وآله وما ولد الحسين بعد فقال له يولد لك غلام تقتله امتك من بعدك فقال يا جبرئيل لا حاجة لي فيه فخاطبه ثلاثا ثم دعا عليا فقال له ان جبرئيل " ع " يخبرني عن الله عز وجل انه يولد لك غلام تقتله أمتك من بعدك فقال لا حاجة لي فيه يارسول الله فخاطب عليا " ع " ثلاثا ثم قال انه يكون فيه وفي ولده الامامة والوراثة والخزانة، فارسل إلى فاطمة عليها السلام ان الله يبشرك بغلام تقتله أمتى من بعدي فقالت فاطمة ليس لي حاجة فيه يا أبة فخاطبها ثلاثا ثم أرسل إليها لابد أن يكون فيه الامامة والوراثة والخزانة فقالت له رضيت عن الله عز وجل فعلقت وحملت بالحسين فحملت ستة اشهر ثم وضعته ولم يعش مولود قط لستة أشهر غير الحسين بن علي وعيسى بن مريم عليهما السلام فكفلته أم سلمة وكان رسول الله يأتيه في كل يوم فيضع لسانه في فم الحسين " ع " فيمصه حتى يروى فانبت الله تعالى لحمه من لحم رسول الله صلى الله عليه وآله ولم يرضع من فاطمة عليها السلام ولا من غيرها لبنا قط فلما انزل الله تبارك وتعالى فيه (وحمله وفصاله ثلاثون شهرا حتى إذا بلغ أشده وبلغ أربعين سنة قال رب أوزعني ان اشكر نعمتك التي انعمت علي وعلى والدي وان اعمل صالحا ترضاه واصلح لي في ذريتي) فلو قال أصلح لي ذريتي كانوا كلهم أئمة لكن خص هكذا.
Some of you may remember my thread on the sacrifice of Husayn. I wanted to point out some of the parallels between Jesus and Husayn, which this hadith seems to delineate. Both were born miraculously with shortened pregnancies. Mary is called al-'adra, because she was a virgin, and Fatima was called al-Batool, which is a similar title indicating purity (she did not menstruate). Both mothers were the best of women of the world, known for their modesty and spoken to by angels. The angel Gabriel announced the birth of both Jesus and Husayn. When Husayn is born, he suckles meat and nor milk - which is a popular biblical expression which refers to the consumption of higher knowledge. Both were granted knowledge as children. Fast forward to the sacrifice - one hadith says that the divine government was initially promised for Husayn, making him a messiah figure, until bada' took place. When Husayn was beheaded, those who mourn and associate with him are absolved of their sins. The final Mahdi is a descendant of Fatima just as the Messiah is the descendant of Mary.