Maliks Muwatta Book 28, Hadith Number 52.

Section : Marriage in General.

Yahya related to me from Malik from Zayd ibn Aslam that the Messenger of Allah, may Allah bless him and grant him peace, said, “When you marry a woman or buy a slave-girl, take her by the forelock and ask for baraka. When you buy a camel, take the top of its hump, and seek refuge with Allah from Shaytan.”