The companions of the Prophet [s] competed with one another to win the hand of Fatimah Al-Zahra [a], his only surviving child. They all knew the great status and high position she enjoyed in Islam. She was part of the Chosen Prophet [s], his beloved daughter, and the chief of Women of the World.
The Messenger of Allah [s] turned down all his companions' offers to marry Fatimah [a].
One day Imam Ali [a] was told of some of the companion's proposals. He heard of the Messenger's objection to her marriage to any of his companions. He felt a desire to go to the Messenger [s] and ask for his daughter's hand.
Before Imam Ali's [a] call on the Prophet [s], to tell him of his desire, Jibr'il [a] had informed the Messenger [s] of the command of Allah, the Exalted and High, to marry Fatimah to Ali [a].
The Divine command, as related by the Holy Revelation, was:
"...O Muhammad Allah, the Most high, sends His greeting to you, and says to you: "I have certainly married Fatimah, your daughter, to Ali bin Abi Talib in heaven. So marry her to him on the earth." 
Imam Ali [a] knocked on the door of the room of Um-Salamah, may Allah be pleased with her. The Messenger of Allah [s] was inside. The Messenger of Allah [s] told him to come in. Imam Ali [a] seated himself next to the Messenger [s] who said to him:
"I see that you have come on business - Tell me about it. Unburden your soul. Any of your requests are granted..."
Imam Ali [a] told his dear leader that he desired Fatimah's hand. On hearing this, the Prophet's face lit up. He went to Al-Zahra [a] to tell her of Ali's request. By doing so, he set an eternal Islamic concept that marriage should be based on mutual consent and agreement, so that the future family would be built on co-operation, love and peace.
The Messenger of Allah said to his daughter:
"Ali bin Abi-Talib is known to you, in his closeness (to us), his merits and profession of Islam...he talked about you. What do you say?"
Fatimah al-Zahra [a] was too shy to say a word. Silence fell on the room and lingered.
The Prophet [s] kept looking at her countenance. Satisfaction and consent were clearly drawn on it. Presently, he went out, repeating from the depths of his pure heart:
Allah is great! Her Silence signals her consent!"
As soon as he returned to Imam Ali [a], the Prophet [s] asked him:
"Do you have anything with which I marry you (to Fatimah)?"
Once more, the Messenger [s] established an Islamic rule for his ummah throughout its generations which stipulates that the man should import the dowry to his wife as the first sign of maintenance, and of his responsibility of managing the affairs of the family.
Imam Ali had nothing beside his sword, a camel for watering his field, and his coat of mail. He told the Prophet [s] of it. The Prophet [s] said:
"As for the sword, you cannot do without it; with it you strive in the way of Allah and fight the enemies of Allah. With your camel you water your date-palms and on it bring water to your family. When you travel you carry luggage on it."
He ordered Imam Ali [a] not to sell his sword and camel but allowed him to sell his coat of mail which was given to him by the Prophet [s], to protect him from the strikes of the enemies.
Imam Ali [a] sold his coat of mail and brought the money to the Messenger of Allah [s] to buy the bride's trousseau.
The Holy Prophet [s] delivered the money to Bilal, Salman and Um-Salamah. They were assigned with the task of buying the needed furniture, perfumes, and clothes. They bought good, simple things.
The Messenger of Allah [s] wanted to inform the Muslims of al-Zahra's betrothal to Ali [a]. He gathered some of his companions to witness the ceremony of the blessed contract of marriage. He addressed them in the following words:
"Praise be to Allah, Who is praised through His favours, worshipped through His power, obeyed through His authority. He is the One feared, due to His trials and punishment, Whose order is executed in His heavens and earth. He created the creatures by His power, distinguished them with His laws, strengthened them with His religion, and honoured them with His Messenger, Muhammad. Allah, may His name be blessed, and His greatness be high, made marriage an attached lineage and an ordained duty by which He solidified family ties and drew people together. He, the Mighty, says:
"And He it is Who has created man from the water then. He has made for him blood-relationship and marriage-relationship and your Lord is Powerful."
Holy Qur'an (25:54)
"Allah's command certainly is executed as His decree. And His decree is obeyed as it is His will. Every decree is issued at a certain time, and every time has a duration, and every duration is fixed. Allah confirms or abrogates what he pleases. His is the Eternal Book. Allah, the Most High, ordered me to marry Fatimah, the daughter of Khadijah, to Ali bin Abi Talib. Bear witness that I have married him (to Fatimah) with a dowry of four hundred mithqals (unit of weight equal to about 5 grams) of silver. That is, it Ali bin Abi Talib agrees to that."
Then he called for a dish of dates. It was placed in front of the gathering.
"Partake of it," the Prophet [s] ordered, and they ate.
All were eating when Imam Ali [a] entered. The Prophet [s] smiled. Then he said: "Allah has ordered me to give to you Fatimah, in marriage with a dowry of four hundred mithqals of silver if you agree to it."
"I agree to it, O Messenger of Allah," Ali replied.
Anas said: "The Prophet said: 'May Allah strengthen the bond that connects you, make your grandfather happy, bless you, and cause you to produce much good.'"
"By Allah", Anas said, "He caused them to produce much good." 
Before one month had slipped by after the ceremony of the contract of marriage, Aqeel bin Abi Talib, may Allah be pleased with him, contacted his brother, Imam Ali [a], urging him to consummate the marriage.
"Why do you not?" he asked. "Ask the Messenger of Allah [s] to bring her (to your house), so that your happiness, by your union, will be completed."
They agreed to approach the Messenger of Allah [s] on the matter. But before doing anything, they met with Um-Ayman Barakah, the daughter of Tha'labah, a respected woman and consulted her. She suggested that she would talk about it to the mothers of the faithful (Prophet's wives), who would, in turn, talk to the Messenger of Allah [s].
The women met with the Prophet [s]. Um-Salamah, on behalf of them, explained the matter to the Messenger of Allah [s]. He sent for Ali. When he came, the Prophet asked him:
"Do you want your wife to be brought to your house?"
"Yes," the Imam replied.
"With pleasure." the Messenger [s] agreed. Then the Noble Prophet [s] asked Imam Ali [a] to make a feast for the faithful. The wives of the Prophet [s] themselves cooked the food. The guests enjoyed it.
Then the Messenger of Allah [s] ordered Um-Salamah and the rest of his wives to take Fatimah to her new house. A procession presently started off led by the Prophet [s] chanting: "There is no god but Allah," and "Allah is great."
The wives of the Prophet [s] recited some verses from the Holy Qur'an in honour of the occasion.
After the wedding ceremony, the Messenger of Allah [s] came to congratulate Imam Ali [a]. He said to him:
"May Allah bless you on account of the daughter of the Messenger of Allah."
He took a bowl of water, recited some Qur'anic verses over it, and ordered Imam Ali and Al-Zahra [a] to drink from it. Then he sprinkled a bit of it on their heads and faces and held his hands up in prayer:
"O Lord! They are the most beloved of the creatures to me. Bless their offspring and protect them. I command them and their descendants into Your protection from the accursed Satan."
Thus glory dwelt in the most honoured house. The school of Imamate was built in the shade of the revelation and the message. It was made under the care of Allah, in the light of His Shari'ah and His righteous path. These ceremonies speak volumes of Islam's simplicity and ease. It is Islam that responds to the needs of the spirit and the body. It doesn't flee in the face of human nature. It is harmonious with life, and the status quo, with no pretension, imposition or injustice.
 Al-Hafidh Muhibul-Deen al-Tabari (died 894 A.H), Dhakha'ir al-Uqba (Treasures of the Hereafter), 1387 A.H/1967 AD ed., p.32.
 Ibid., p.30.