Answer:

Introduction:
The person who ordered that a man should marry only one wife and could marry another only when the first wife was barren was Akbar, the Mughal emperor. Akbar was known for his liberal policies and religious tolerance, and he implemented several social reforms during his reign to promote harmony and equality among different communities.

Akbar's Reforms:
During the Mughal era, polygamy was prevalent among the ruling class, and men were allowed to have multiple wives. However, Akbar realized that this practice often led to conflicts and inequalities within families, and he wanted to bring about a change in this system. He believed that restricting the number of wives a man could have would promote stability and equality in marriages.

Marriage Reforms:
To implement this change, Akbar introduced the law that a man could only have one wife, and if she was barren and unable to bear children, he could marry another woman. This law was aimed at ensuring that men would not take multiple wives simply for personal desires, but only when there was a genuine need for a child.

Reasoning behind the Reforms:
Akbar's decision to enforce this law was driven by his belief in justice and equality. He wanted to ensure that women were treated fairly and that their rights were protected. By allowing men to marry multiple wives only in case of infertility, Akbar sought to prevent the mistreatment of women and reduce inequalities within families.

Impact of the Reforms:
Akbar's marriage reforms had a significant impact on society. They promoted monogamy and discouraged the practice of having multiple wives for personal reasons. This not only brought stability to marriages but also reduced conflicts within families. Additionally, the reforms gave women more rights and protection, as they were no longer subjected to the mistreatment that often occurred in polygamous relationships.

Conclusion:
In conclusion, Akbar, the Mughal emperor, ordered that a man should marry only one wife and could marry another only when the first wife was barren. This reform was aimed at promoting stability, equality, and justice within families. Akbar's progressive policies have had a lasting impact on Indian society and continue to be recognized and appreciated to this day.