Maliks Muwatta Book 28, Hadith Number 24.

Section : What is Not Permitted in Marriage in General.

Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, forbade shighar, which meant one man giving his daughter in marriage to another man on the condition that the other gave his daughter to him in marriage without either of them paying the bride-price.