If one of you marries a woman or buys a slave, he should say: "O Allah, I ask You for the good in her, and in the disposition You have given her; I take 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. Abu Dawud said: Abu Sa'id added the following words in his version: He should then tale hold of her forelock and pray for blessing in the case of a woman or a slave. (Using translation from Abū Dāʾūd 2160)
"إذا تزوَّج أحدُكمُ امرأة أو اشترى خادمًا، فلْيقُلْ: الَّلهُم إني أسألك خيرها وخيرَ ما جبلتها عليه، وأعوذُ بك من شرها وشر ما جبلتها عليه، وإذا اشترى بعيرًا فْليأخذْ بذروة سنامه وليقلْ: مثل ذلك".