The reports of the seerah (Prophet’s biography) indicate that Khadeejah bint Khuwaylid (may Allah be pleased with her) was a determined and intelligent woman, and she was also rich and had several kinds of trade. She had been widowed when her husband Abu Halah died.
Before the advent of Islam, Khadija was a businesswoman who hired men to trade goods on her behalf. Through enquiries and through what she had heard from the people, Muhammad (peace be upon him) was an excellent choice for the kinds of work she required. She sent someone to him with an offer of work, and he (peace be upon him) agreed to that.
By having Muhammad (peace be upon him) under her employment, she was thus able to not only testify to but be affected by the unique character and personality of the Prophet peace be upon him. Due to this trustworthy and sincere nature he was thus an excellent candidate for marriage. He was thus offered so via Nafeesah bint Maniyyah which he agreed to via his uncle Hamzah (may Allah be pleased with him). According to sound reports, the marriage was arranged by Khadeejah’s (may Allah be pleased with her) father – Khuwaylid.
It would be incorrect for anyone to make the assumption that some kind of inappropriate relationship between the Prophet (peace be upon him) and Khadeejah (may Allah be pleased with her) existed before marriage. Although adultery existed plentifully in Prophet’s (peace be upon him) pre-Islamic environment, the sanctity of marriage was still known, the morals of the Prophet (peace be upon him) were well known even before the message of Islam. Further more, it would be irrational to suggest this when one realises that Allah protected the Prophet (peace be upon him) from everything that may have detracted from his noble message or which was contrary or ill-befitting to the high-station which the Prophet (peace be upon him) possessed after revelation.
Even if such a thing had happened, the idolatrous Quraysh would not have kept quiet about it. They would have used as a means to stir dissension and shame with which to tarnish his reputation. Rather, he was known to all before becoming a prophet as al-Saadiq (the honest one) and al-Ameen (the trustworthy one). Casting aspersion regarding his chastity was something which they did not even think to do.
In conclusion, one should keep in mind that the Prophets (peace be upon them) – every single one of them – are the best and most perfect of humanity. Allah does not simply choose anyone to convey his, rather, only those who are fit for it are given revelation: “Allah knows best with whom to place His Message” [al-An’aam 6:124]
Nadwi, Sayyed Abul Hasan, Muhammad The Last Prophet – A model for all time, UK Islamic Academy, Leicester, UK, 2006, pg. 24-25.