Muwatta Imam Malik Book of Marriage, Hadith 52

Yahya related to me from Malik from Zayd ibn Aslam that the Messenger of Allah ﷺ 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."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " إِذَا تَزَوَّجَ أَحَدُكُمُ الْمَرْأَةَ أَوِ اشْتَرَى الْجَارِيَةَ فَلْيَأْخُذْ بِنَاصِيَتِهَا وَلْيَدْعُ بِالْبَرَكَةِ وَإِذَا اشْتَرَى الْبَعِيرَ فَلْيَأْخُذْ بِذِرْوَةِ سَنَامِهِ وَلْيَسْتَعِذْ بِاللَّهِ مِنَ الشَّيْطَانِ " .