Hadith 511470
Chapter 28: Marriage - كتاب النكاح
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا تَزَوَّجَ أَحَدُكُمُ الْمَرْأَةَ أَوِ اشْتَرَى الْجَارِيَةَ فَلْيَأْخُذْ بِنَاصِيَتِهَا وَلْيَدْعُ بِالْبَرَكَةِ وَإِذَا اشْتَرَى الْبَعِيرَ فَلْيَأْخُذْ بِذِرْوَةِ سَنَامِهِ وَلْيَسْتَعِذْ بِاللَّهِ مِنَ الشَّيْطَانِ " .
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."
Reference Muwatta Malik 511470
USC-MSA web (English) reference : Book 28, Hadith 52