All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Narrated Al-Miswar bin Makhrama: "Ali demanded the hand of the daughter of Abu Jahl. Fatima heard of this and went to Allah's Messenger (PBUH) saying, "Your people think that you do not become angry for the sake of your daughters as `Ali is now going to marry the daughter of Abu Jahl. "On that Allah's Messenger (PBUH) got up and after his recitation of Tashah-hud. I heard him saying, "Then after! I married one of my daughters to Abu Al-`As bin Al- Rabi` (the husband of Zainab, the daughter of the Prophet (PBUH) ) before Islam and he proved truthful in whatever he said to me. No doubt, Fatima is a part of me, I hate to see her being troubled. By Allah, the daughter of Allah's Messenger (PBUH) and the daughter of Allah's Enemy cannot be the wives of one man." So `Ali gave up that engagement. 'Al-Miswar further said: I heard the Prophet (PBUH) talking and he mentioned a son-in-law of his belonging to the tribe of Bani `Abd-Shams. He highly praised him concerning that relationship and said (whenever) he spoke to me, he spoke the truth, and whenever he promised me, he fulfilled his promise. I do not make a legal thing illegal, nor do I make an illegal thing legal, but by Allah, the daughter of Allah's Messenger (PBUH) and the daughter of the enemy of Allah, (i.e. Abu Jahl) can never get together (as the wives of one man) " {Related by Bukhari}.
Amongst the fundamentals of the creed of Ahlus Sunnah wal Jamaah is that Allah has preserved the Prophet (PBUH) from violating the teachings of Sharia. On the contrary, Allah entrusted him (PBUH) with conveying and applying these teachings. In this regard, Allah says, "O Messenger. proclaim the (message) which hath been sent to thee from thy Lord. If thou didst not, thou wouldst not have fulfilled and proclaimed His mission. And Allah will defend thee from men (who mean mischief). For Allah guideth not those who reject Faith." {Al-Mai`dah, 67}.
His refusing to grant Ali permission for second marriage isn`t a breach of justice or none adherence to the rules of Sharia for he (PBUH) doesn`t make a legal thing illegal as indicated in the above narration. Scholars have given many an interpretation of the above narration. For example, it was stipulated in the marriage contract of Fatima and Ali that he doesn`t marry a second wife. Therefore, it was imperative that Ali meets this condition. Scholars have concluded this from the Prophet`s reference to a son-in-law of his belonging to the tribe of Bani `Abd-Shams. He highly praised him concerning that relationship and said (whenever) he spoke to me, he spoke the truth, and whenever he promised me, he fulfilled his promise.
Moreover, An-Nawawi said, "When the Prophet (PBUH) said, " I do not make a legal thing illegal," this indicates that Ali`s marriage to the daughter of Abu Jahel is lawful, but he (PBUH) forbade that the daughter of Allah's Messenger (PBUH) and that of Allah's Enemy be the wives of one man for two reasons mentioned in the above narration. First, Fatima will be harmed. Second, she may be put to trial in regard to religion." {Shareh Sahih Muslim, V.3:P.16}.
In addition, the Prophet (PBUH) felt sorry for Ali because the latter may incur sin form the harm that could befall the Prophet (PBUH) because of this marriage. "Ibn At-Teen said, "The most correct interpretation of this narration is that the Prophet (PBUH) forbade that Fatima and the daughter of Abu Jahel get together as the wives of Ali because this will harm him (PBUH), and this is forbidden by scholarly consensus. However, had Ali not been married to Fatima, his marriage to the daughter of Abu Jahel would have been lawful. Since bringing both together as wives of Ali leads to harming the Prophet (PBUH) because of Fatima being harmed, it wasn`t permitted. Others claimed that the context of the story gives the impression that it was lawful for Ali to marry the daughter of Abu Jahel, but the Prophet (PBUH) forbade Ali from that to avoid harming Fatima and Ali accepted in compliance with the Prophet`s order. Moreover, it can`t be excluded that this (No second marriage for husbands` of Prophet`s daughters) is a characteristic of the Prophet (PBUH) and likely to be special for Fatima (May Allah be pleased with her)."
In conclusion, a Muslim must stick to decisive proof, which is the infallibility of the Prophet (PBUH) and his wisdom when it comes to dealing with worldly matters. Thus, whomever truly loves the Prophet (PBUH) must approve of whatever he (PBUH) loves, chooses and is pleased with, and this is among the signs of faith. The evidence on this is that Allah the Almighty says {What means}, " What God has bestowed on His Apostle (and taken away) from the people of the townships,- belongs to God,- to His Apostle and to kindred and orphans, the needy and the wayfarer; In order that it may not (merely) make a circuit between the wealthy among you. So take what the Apostle assigns to you, and deny yourselves that which he withholds from you. And fear God; for God is strict in Punishment." {Al-Hasher, 7}. And Allah the Almighty knows best.