Ibn 'Umar (RA) said that Allah's Messenger (ﷺ) prohibited Shighar which means that a man gives his daughter in marriage on the condition that the other gives his daughter to him in marriage without any dower being paid by either.
Abu Hurairah (RA) reported that Allah's Messenger (ﷺ) prohibited Shighar. Ibn Numair added: Shighar means that a person should say to the other person: Give me the hand of your daughter in marriage and I will (in return) marry my daughter to you; or marry me your sister, and I will marry my sister to you.