Khadijah appears in the sources first as a businesswoman. She belonged to the Quraysh, the ruling tribal confederation of Mecca, had been married before, and financed caravan trade to Syria, engaging agents to travel with the goods and take a share of the profit. Mecca's position depended on that trade, and a woman conducting it on her own account was unusual without being unheard of.
She hired Muhammad, then a young man of good family and no property, to take a caravan north. The accounts have her servant Maysara returning with a favourable report of his conduct in the dealings, and the marriage proposal following, initiated by her through an intermediary. He is generally given as about twenty five at the time. Her own age is reported as forty in the best known account, and other early reports give twenty eight, so the figure is not fixed.
The marriage lasted until her death, roughly twenty five years, and he took no other wife while she lived, which is a fact both traditions note and to which later discussion returns often. Their children included several daughters, among them Fatimah, and sons who died in infancy. Her household also included Zayd ibn Haritha, whom she had given to her husband and who was subsequently freed and adopted, and their young cousin Ali, who was brought into the house during a period of hardship in his own family.