'Amr b. Shu'aib, on his father’s authority, said his grandfather told how the Prophet (ﷺ) said that when anyone of them married a woman, or bought a servant he should say, “O God, I ask You for the good in her and in the disposition You have given her, and I seek refuge in You from the evil in her and in the disposition You have given her.” When he buys a camel he should take hold of the top of its hump and say the same kind of thing. In a version regarding a woman and a servant it says he should take hold of her forelock and make supplication for a blessing. Abu Dawud and Ibn Majah transmitted it.

وَعَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جَدِّهِ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا تَزَوَّجَ أَحَدُكُمُ امْرَأَةً أَوِ اشْتَرَى خَادِمًا فَلْيَقُلْ اللَّهُمَّ إِنِّي أَسْأَلُكَ خَيْرَهَا وَخَيْرَ مَا جَبَلْتَهَا عَلَيْهِ وَأَعُوذُ بِكَ مِنْ شَرِّهَا وَشَرِّ مَا جَبَلْتَهَا عَلَيْهِ وَإِذَا اشْتَرَى بَعِيرًا فليأخُذْ بِذروةِ سنامِهِ ولْيَقُلْ مِثْلَ ذَلِكَ» . وَفِي رِوَايَةٍ فِي الْمَرْأَةِ وَالْخَادِمِ: «ثُمَّ لْيَأْخُذْ بِنَاصِيَتِهَا وَلْيَدْعُ بِالْبَرَكَةِ» . رَوَاهُ أَبُو دَاوُد وَابْن مَاجَه