‘Abdullāh ibn ‘Umar (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) prohibited Shighār marriage. Shighār marriage means that a man gives his daughter in marriage to another on condition that the other gives his daughter to him in marriage without any dower being paid by either.
The basic principle in a marriage contract is that it is not fulfilled unless it includes a dowry for the woman which she receives in return for offering herself to her husband (for sexual enjoyment). For this reason, the Prophet (may Allah's peace and blessings be upon him) prohibited this type of pre-Islamic marriage called Shighār, by which the guardians used to wrong women under their care. They would marry off the women under their care without a dowry which benefits the women. Rather, they used those women for fulfilling their own desires and lusts by giving the woman under their care in marriage to a husband, in return for marrying the woman under the care of that husband without a dowry as well. This type of marriage involves injustice, because the guardians make their womenfolk lawful to men in a way other than that legislated by Allah. Anything of this sort is impermissible and invalid.