Muwatta Malik 1144

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