"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. [Al-Bukhari]
"عن عبد الله بن عمر -رضي الله عنهما-: «أن رسول الله -صلى الله عليه وسلم- نهى عن الشِّغَارِ». [صحيح] - [متفق عليه.]"