I heard a hadith which says that once Hazrat Ali (rta) asked permission from Muhammad (sws) for second marriage and the Prophet (sws) refused to grant him permission. Could you please confirm the hadith and, why Muhammad (sws) refused to grant Hazart Ali (rta) his request?
Here is one translation of the hadith.
Narrated by Ali ibn al-Husayn:
"I heard Allah's Apostle who was on the pulpit, saying, 'Banu Hisham bin Al-Mughira have requested me to allow them to marry their daughter to Ali bin Abu Talib, but I don't give permission, and will not give permission unless 'Ali bin Abi Talib divorces my daughter in order to marry their daughter, because Fatima is a part of my body, and I hate what she hates to see, and what hurts her, hurts me.'" (Bukhari, No. 4887)
"Ali demanded the hand of the daughter of Abu Jahl. Fatimah heard of this and went to Allah's Messenger saying, 'Your people think that you do not become angry for the sake of your daughters as `Ali now is going to marry the daughter of Abu Jahl.'
The hadith appears in reliable works and appears to be probable.
On that, the Messenger got up and after his recitation of Tashahhud (witnessing the oneness of the Creator and the prophethood of His Final Messenger) I heard him saying, 'I married one of my daughters (Zainab) to Abu Al-`Aas ibn Ar-Rabi` before Islam and he proved truthful in whatever he said to me. No doubt Fatimah is part of me; I hate to see her troubled. By Allah, the daughter of Allah's Messenger and the daughter of Allah's enemy cannot be the wives of one man.'" (Bukhari, No. 2900)
We understand that it is not a legal prohibition but expression of love of a father for his daughter especially when the son in law is pondering over marrying into the family which has caused the concerned father great harm. The Qur'an clearly allows adult male and female believers to marry persons of their choice. It also does not prohibit second marriage. Therefore, we cannot take it as a religious or legal ruling.