Cognitive
Without Khadija's money and family influence, Mohamed's project Islam would have limited success or failed like many others did at that time. As for not marrying other women while he was married to her requires to understand from the premise of a simple logic of a "sugar mummy" refusing her "trophy husband" to bring other women.
While he was meditating in cave of Hira, the Angel Jibreel (AS) came to the Prophet Muhammad (SAW) and revealed to him the first verses of the Quran and declared to him that he was to be a Prophet. The experience terrified the Prophet Muhammad (SAW), and he ran home, jumping into Khadijah’s (RA) arms crying,
“Cover me! Cover me!” She was startled by his terror, and after soothing and comforting him for a while, the Prophet was able to calm down and relate to her his experience.
The Prophet (SAW) feared he was losing his mind or being possessed. Khadijah (RA) put all his fears to rest:
“Do not worry,” she said, “for by Him who has dominion over Khadijah’s soul, I hope that you are the Prophet of this nation. Allah would never humiliate you, for you are good to your relatives, you are true to your word, you help those who are in need, you support the weak, you feed the guest and you answer the call of those who are in distress.”
She then took him to her cousin, Waraqah ibn Nawfal – a scholar well-versed in the Judeo-Christian scripture – and he confirmed to the Prophet (SAW) that his experience was Divine and he was to be the Last Prophet.
After his ministry began, and the opposition of his people became harsh and brutal, Khadijah (RA) was always there to support the Prophet Muhammad (SAW), sacrificing all of her wealth to support the cause of Islam. When the Prophet Muhammad (SAW) and his family was banished to the hills outside of Makkah, she went there with him, and the three years of hardship and deprivation eventually led to her death. The Prophet Muhammad (SAW) mourned her deeply, and even after her death, the Prophet Muhammad (SAW) would send food and support to Khadijah’s friends and relatives, out of love for his first wife.
Once, years after Khadijah (RA) died, he came across a necklace that she once wore. When he saw it, he remembered her and began to cry and mourn. His love for her never died, so much so, that his later wife Ayesha once felt jealous of her. Once she asked the Prophet Muhammad (SAW) if Khadijah (RA) had been the only woman worthy of his love. The Prophet replied:
“She believed in me when no one else did; she accepted Islam when people rejected me; and she helped and comforted me when there was no one else to lend me a helping hand.”
Much has been made and said about Prophet Muhammad’s multiple marriages. There are many who smear the Prophet as a womanizing philanderer, citing his multiple marriages. This is absolute propaganda. As a response to those who malign the Prophet, If the Prophet were anything of the sort, he would have taken advantage of his youth to do such a thing. But he did not! At a time when it was a common custom to have multiple wives, the Prophet did not marry anyone else while he was with Khadijah (RA).
Only between the age of fifty and his death at sixty-two did Prophet Mohammed take other wives. Most of these wives were widows, whom the Prophet married to care after them, or they were they were the daughters of prominent Arab chieftains, so that the Prophet could form a cohesive Muslim society out of a fiercely tribalistic (and barbaric) Arab culture. The smears against the Prophet fall flat on their faces once the light of truth shines brightly upon them.
For his human and natural needs, the Prophet (SAW) married twice. His first marriage was with Hadhrat Khadija (RA). During this time, he did not marry another woman. After her death, he married Hadhrat Sawdah (RA). The purpose of this marriage was purely a human need, that is after the death of Hadhrat Khadija (RA) his two younger daughters were left alone and he needed somebody to look after them. Therefore, he married Hadhrat Sawdah (RA) who was 50 at the time of marriage and so was the Prophet (SAW).
In the capacity of a Prophet (Nabi), he married four women, namely Hadhrat Ayesha (RA), Hadhrat Hafsa (RA), Hadhrat Zaynab bint-i-Khazeema (RA) and Hadhrat Ume Salama (RA). The Prophet’s wives were also made associates in his prophetic mission. Especially for this purpose, he married Hadhrat Ayesha (RA) and it is a known fact that in fulfilling this responsibility she had no match. She became the mentor of the Ummah after the Prophet (SAW)’s death. The rest of the three marriages were the result of social requirements. This social requirement was, taking care of widows and orphans as the Quran directed to do in Surah Al-Nisaa. Taking care of widows and orphans was a very big responsibility. It became necessary that the Prophet Muhammad (SAW) set an example for the Muslims in this regard to give them an incentive, as he was, in the capacity of a Nabi an example for the Muslims to follow.
The divorced women till today, are generally looked down upon in popular estimation, and this was a case in which a freed slave divorced a lady of high birth. By also taking such a divorced woman as his wife, the false notion that divorce degraded women was removed as well. Thus by this act, to which he was morally bound because the lady had been at first offered in marriage to him, he elevated the whole class of divorced women who would otherwise suffer life-long humiliation in society.
http://navedz.com/prophet_muhammad_saw__khadijah_ra_the_greatest_love/