The exalted Prophet was now also Head of the State. Quite a few Muslims had been killed in battles and by persecution. There were women who accepted Islam while their husbands did not. The Qur’an does not allow a Muslim woman to remain wedded to a Non-Muslim. In these circumstances, there were many women and their children who needed shelter. The Prophet (S) and his companions accommodated them in their homes. To prevent slander, these widows and divorcees simply signed marriage contracts in their new households.
To emphasize the point again, the exalted Messenger married only Hazrat Khadija when he was 25, and she was 40. They lived an ideal married life for 25 years. Hazrat Khadija died in Makkah at 65. Three years after her death and soon after migration to Madinah in AH 1, Muhammad (S) married Hazrat Ayesha, a sister of Hazrat Abu Bakr. She was then 48.
During the blessed times, the Central Government run with Shura used to issue a deed of marriage to all women seeking asylum with Rasool (S) and Sahaba Kiraam in order to prevent slander. This is the reason why the Qur’an mentions the exalted Prophet's wives in plural. Please reflect on the many shades of the meaning of Nikah. Also consider why NONE BUT Hazrat Khadijah bore any children to the exalted Prophet.
Maria, the bondwoman reportedly "gifted" to the exalted prophet by the Egyptian ruler, is nothing but a malicious fabrication. How could the exalted prophet accept bondwomen and slaves when the Qur’an was emancipating them? One might assume well and think, "Well, in order to grant them freedom." But our brilliant historians insist that Maria always remained a concubine!